Beat butter and sugar in a large bowl with an electric mixer.

Add the salt, egg, lemon zest and vanilla; beat well. With the mixer at low speed, add the flour 1 cup at a time. Beat only until a soft dough forms.

Press dough into the crock of a casserole crock (preferred) or a 6-7 quart oval slow cooker.

Spread lemon curd evenly on top of dough.

Place 2 layers of paper towels on top of the crock (don’t let them touch the top of the bars) and place lid on slow cooker. The lid will secure the paper towels and prevent them from falling on the lemon bars.

Set slow cooker to high and cook for 2-3 hours (mine took 3 in the casserole crock). Bars are done when the corners (edges) are beginning to brown and the center is set–bars will continue to cook during the cooling.

Cool completely in the slow cooker. Cut into bars and dust with confectioner’s sugar.

Yield varies as to size/shape cooker used. The casserole crock yielded 12 bars.