- Course: Dessert
- Skill Level: Moderate
- Cost: Inexpensive
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Can be made ahead of time.
Wonderfully creamy and brimming with the flowery, tangerine flavor of Meyer lemons, this lemon curd is an excellent filling for tarts or a delicious condiment for toast and sweet pastries. This curd has a very high proportion of egg yolks, which lends it an intense flavor and a smooth consistency. If you cannot find meyer lemons you can easily substitute regular lemons. Try adding 1 tablespoon of tangerine zest to make up for the missing Meyer lemon flavor.
Although you only need the zest of 1 lemon in this recipe, do not throw away the precious rinds from the remaining meyer lemons. Before you slice and juice the lemons, use a peeler to remove the zest. Julienne the zest into thin spaghetti-like strands and candy. Use the candied zest to garnish the tart or as an added note of flavor on mini fresh berry tarts filled with either lemon or passion-fruit curd.
Prepare and bake the Sweet Tart crust.
Make the lemon curd (see "The unique consistency of citrus curd" in Notes, below):
In the bowl of a bain-marie, whisk together the egg yolks, whole egg, and sugar. Add the lemon juice, lemon zest, and salt. Whisk briskly until the mixture has thickened, doubled in volume, and holds the lines of a whisk, 5 to 10 minutes.
Remove the curd from the heat and pass through a fine-mesh strainer into a bowl. Discard the zest. Place the bowl in an ice bath and let cool until warm to the touch. Thoroughly whisk in the butter. At this point you can chill or bake the lemon curd.
Bake the lemon tart:
Preheat the oven to 325°F. Pour the lemon curd into the prepared tart shell. Place the tart on a cookie sheet and bake until the custard sets, 10 to 15 minutes. To test if the custard is set, gently tap the tart ring; if the center does not jiggle, the custard is set. If you have made the curd ahead of time and refrigerated it, the tart will need a few extra minutes in the oven to set.
Serve the tart at room temperature. It is delicious on its own, but whipped cream or crème fraîche and a few raspberries or strawberries make great accompaniments. I also recommend the spiced Mandarin Ice Cream, Basil Ice Cream, Guava Sorbet, or Pineapple-Rosemary Sorbet. You can also use the curd as a condiment or as a filling for mini tartlets, topped with fresh berries and candied zest.
Storage: The curd, well sealed and refrigerated, will keep for up to 1 week. The finished tart is best if served the day it is made but will keep, covered and refrigerated, for up to 3 days.
Meyer lemons: Available from November to March, meyer lemons have a smooth-skinned, deep matte yellow appearance. A cross between a lemon and an orange, the meyer lemon is slightly sweeter (less acidic) than a regular lemon. The most distinctive feature of this hybrid is the zest, which has a flowery tangerine-like aroma and imparts incredibly round lemony flavor to sweet and savory foods.
Bain-marie is the French cooking term for a metal bowl or container that can sit over or in simmering water to keep the contents of the container or bowl hot—basically, a makeshift double boiler. Fill a pot large enough to hold a medium-sized mixing bowl on top with 1 inch of water and set over low heat. When the water is simmering, set the bowl on top of the pot. If you are using a bain-marie for a sabayon, simmer the water over medium-high heat.
The unique consistency of citrus curds:
Lemon curd, as well as all the other curds such as passion-fruit, lime, and berry curds made with lemon juice, has an utterly unique consistency. Unlike most milk- and wine-based custards, citrus curds are dense, creamy, and very tender, and maintain their texture even if spread with a knife. Curd achieves these unique textural properties through the interplay of its three main ingredients: low pH citrus juice, sugar, and egg yolks--the latter two in significantly higher proportions compared to other custards. Custards achieve their creamy consistency through the process of egg proteins forming structures that hold liquid--in other words, forming gels.
Acid changes the chemical processes fairly dramatically by changing how proteins bond and thus gel. The addition of acid to eggs causes three principal simultaneous biochemical changes in the properties of the eggs: (1) the ions (positively and negatively charged molecules, of which there are millions upon millions) in solution from the acidic lemon juice break the chemical bonds in individual proteins, causing them to begin to denature or unwind from their ball-like shape; (2) additional ions of the same type neutralize the overall charge of the proteins, allowing the not fully denatured proteins to be more likely to interact and bond in solution; and (3) acid reduces the likelihood of the formation of disulfide bonds, a strong and rare bond in proteins, but one presumed to be more prevalent in eggs, thereby making acidic protein gels softer, more tender, and less structured. The net result of all three effects is to cause early protein interaction, or bonding, and at the same time to prevent full gelation during and after the addition of heat.
The other two aspects of citrus curds that are unique in comparison with other custards are the high percentage of egg yolks and sugar. The high percentage of egg yolks increases the proportion of egg yolk proteins in the custard, which helps give the curd a thicker, partially gelled tender texture. Also many proteins in egg yolks are lipoproteins; one end of the protein is bonded to an emulsifying fat molecule, one that connects to both water and fat molecules. These emulsifying lipoproteins playa major role in the curd’s overall creamy texture as well.
The high percentage of sugar, added to balance the tartness of the citrus juice, has a more complex consequence. To begin with, the high proportion of sugar is dissolved in the added citrus juice, a proportionately small amount of water, which contributes to the finished curd’s trademark density. Sugar also acts by interfering in protein-to-protein bonding, preventing full gelation.
One of the beneficial results of the added sugar is that sometimes, while you are cooking a lemon curd, it gets so hot that a bubble or two comes to the surface yet the custard remains smooth and glossy, not lumpy, watery, and broken. This characteristic makes it unlike almost all other custards, where boiling temperatures destroy the gel, ruining the dessert.
There’s one thing you need to be careful about, though, in vigorously whisking lemon curd at boiling temperatures. Citrus curd can, if cooked for too long, develop a sandy consistency once it is cooled. This sandiness is due to sugar recrystallization (not, as in other custards, to overcooked eggs). If you whisk the curd over a high temperature for a long period of time, enough of the naturally present water evaporates so that the sugar, as the custard cools, recrystallizes onto itself. This happens because there is simply not enough water remaining for all of the sugar to stay dissolved in it.
Nutritional information does not include Sweet Tart Crust. For nutritional information on Sweet Tart Crust, please follow the link above.