Preheat oven to 350 degrees Fahrenheit. Grease a nine- by 13-inch baking pan.

Blend flour, sugar, and salt in a food processor. Add margarine and pulse until coarse crumbs form.

Press crumbs firmly into pan. Bake until pale gold, approximately 30 minutes.

Sift together flour, baking powder, and salt.

In a separate bowl, beat eggs well; add sugar and vanilla extract and beat until thick.

Stir in the flour mixture and then the jam, until smooth. Spread over crust.

Bake until puffed and dark brown, and a toothpick inserted comes out with soft, moist crumbs attached; about 40 minutes. (Be careful not to over-bake; it will be very dry.) Cool completely.

Sift confectioners’ sugar over bars and cut into small squares.