Butter a 9 x 13 pan and line with parchment paper. Make sure there is overhang on at least two sides so that you can easily pull the bars out of the pan. Preheat the oven to 375°F (190°C).
Use a microplane or box grater to zest the lemons. Cut a lemon in half and squeeze both halves until you have 2 tbsp and 1 tsp of juice. Set aside.
Whisk the flour, baking powder and salt together in a medium bowl.
In a large bowl, cream the butter, Crisco and sugar until it's light and fluffy. Beat in the eggs one at a time, making sure each is well-incorporated. On low speed, mix in the lemon juice and lemon zest.
On low speed, gradually blend in the dry ingredients until just combined.
Spread the dough evenly into the prepared pan and bake for 15 minutes, or until the edges are very lightly browned and the middle is no longer doughy. (It should still be soft.) Let cool in the pan completely.