In a medium bowl, beat the yolks slowly but firmly with a whisk until they become creamy and light yellow in color. Add 2 Tbsp of the lemon juice, the mustard, and salt, and mix well.

In a small bowl, combine the canola and olive oils; then drizzle very slowly into the yolk mixture while whisking constantly. (Be careful not to overbeat.)

Stir the remaining 2 Tbsp of lemon juice into the mayonnaise, then cover and refrigerate for at least 2 hours before using.