Puree Raspberries: Use a hand blender for fresh raspberries or cook frozen raspberries with water until soft. Strain to remove seeds.
1 pound raspberries
Prep Lemon: Wash the lemon thoroughly, soaking if needed to remove pesticides.
Zest & Squeeze: Zest and then juice the lemon.
1/2 lemon
Prep Eggs: Whisk eggs and yolks with sugar in a bowl and set aside.
4 eggs, 2 egg yolks, 3/4 cup sugar
Cook Puree Mixture: Combine raspberry puree, lemon juice, and zest in a pot. Heat until it bubbles then remove from heat.
Temper Eggs: Slowly mix the hot puree into the eggs to avoid curdling. Return the mixture to the pot.
Cook: Stir the mixture on low heat until it noticeably thickens.
Add Butter: Off the heat, add chopped butter and stir until melted and incorporated.
4 oz butter
Strain (Optional): Optionally strain the curd for a smoother texture.
Cover & Cool: Cover the surface with plastic wrap to prevent skin formation.
Refrigerate: Cool to about room temperature, then chill in the refrigerator in a sealed container.