Adjust the oven rack to the middle position and preheat the oven to 325 degrees.

To prepare the batter: Spread the whole almonds on a baking sheet and toast in the oven until lightly browned, about 15 to 20 minutes. Shake the pan halfway through to ensure that the nuts toast evenly.

Turn the oven up to 350 degrees.

In the bowl of a food processor fitted with the steel blade, combine the almonds with half of the granulated sugar and process until it’s the consistency of a fine meal.

In the bowl of an electric mixer fitted with the paddle attachment, cream the butter, orange zest, baking powder, baking soda, and salt on low, 2 to 3 minutes, until softened. Add the remaining sugar and ground nut mixture, and mix on medium about 3 to 4 minutes, until light and fluffy, scraping down the sides of the bowl as needed. Add the eggs, 1 tablespoon at a time, mixing well between each addition. Slowly, pour in the buttermilk and mix on medium, just to combine.

Add the flour in 3 batches, turning the mixer off before each addition and mixing on low until just combined.

Remove the bowl from the mixer and fold in the fruit.

To prepare the topping: In a small bowl, whisk the egg white until frothy. Add the sugar, cinnamon, nutmeg, and almonds.

Fill the pastry bag half full and pipe or spoon the batter into the prepared muffin tin, filling the cups to the rim. Spoon about a tablespoon of topping over each muffin, concentrating the almonds in the center of each muffin.

Bake for about 20 to 25 minutes, until the topping is nicely browned and the muffin is firm to the touch. If the batter has cracked through the topping, gently press it down with your fingertips to deflate.