In a small sauce pot, add the lemon juice, 3/4 cup of the sugar and 3 egg yolks. Whisk until smooth, place on medium heat and bring to a boil, stirring constantly. Cook for 4 minutes. Take off the heat, add in 4 tablespoons of the butter, 1/4 teaspoon of the vanilla and a pinch of salt. Stir to combine, let cool completely.
Repeat the first step but in place of the lemon, use the raspberry puree and use the remaining ingredients as listed in the first step.
Once the curds are cool, layer in an airtight container and store in the refrigerator, enjoy.
Notes
You, of course, do not need to do the layering effect as I have done in this post. If you wish to just mix the two together, place the lemon juice through eggs, whisk everything until combined and cook as listed in the first step. Add all the butter, vanilla and salt. Store the same way.