Raspberry Streusel Bars

This recipe can be made in a standing mixer or a food processor. Frozen raspberries can be substituted for fresh; be sure to defrost them before combining with the raspberry preserves. If your fresh raspberries are very tart, add only 1 or 2 teaspoons of lemon juice to the filling. The bars are best eaten the day they are baked but can be kept in an airtight container for up to 3 days (the crust and streusel will soften slightly with storage).