Preheat the oven to 350. Line 12 holes of a muffin tin with paper cupcake liners.
Beat the butter, coconut oil, and sweetener with an electric mixer until creamy. Mix in the sour cream, eggs, lemon extract, juice, and zest. Mix in the baking mix, salt, and baking powder. Divide between the lined muffin cups.
Bake for 30-35 minutes until the top springs back when lightly pressed with your finger and the edges are golden. Cool completely.
To make lemon curd:
Meanwhile, make the lemon curd. In a small saucepan over medium low heat melt the butter and sweetener. Cook until slightly thickened. Whisk in the egg yolks one at a time. Cook until thick. Add the lemon juice and whisk until smooth. Strain through a fine mesh strainer in case there are any bits of scrambled yolk. Put in a glass bowl or jar and refrigerate until cold.
To make the raspberry frosting:
Put the butter, raspberries, and sweetener in a microwave-safe bowl or the cup of a rocket blender and microwave until warm. Blend in a food processor, blender, or rocket blender until smooth. It will be the same consistency as the lemon curd. Cool until room temp. Beat the heavy cream until stiff peaks form. Gently fold in the raspberry puree. Refrigerate until ready to ice the cupcakes.
Using a small paring knife remove the center of the cupcake. Be careful to leave some on the bottom and not to pierce the paper. Divide the lemon curd between the cupcakes. I used a piping bag to make this easier. Press one fresh or frozen raspberry on top of the curd. Pipe the raspberry whipped cream on top of the cupcakes. If you prefer to spread it put a big blob on top of each and spread it carefully to avoid disturbing the lemon curd and raspberry filling.