Puree the raspberries and put them through a fine strainer to remove the seeds. Measure to make 1 1/2 cup puree, heat it in a non-corroding saucepan, and stir in the sugar and butter. Taste and add the lemon juice if needed. Whisk the eggs and egg yolks just enough to mix them. Then stir in some of the hot puree to warm them. Return to the pan and cook over low heat, stirring constantly, until the mixture is thick- it should reach a temperature of 170°F Chill.