Sift together flour, baking powder and salt in large bowl. Add lard and cut in with pastry cutter or fingertips until the mixture resembles coarse crumbs. In a measuring cup, mix water, egg yolks and lemon juice together and pour over flour mixture. Blend gently with a fork until combined; mixture will be very moist.
Divide dough in half. Roll or pat one half of dough directly into 9" by 13" jelly roll pan, bringing dough slightly up the edges. I patted with my hands, you could also try a mini roller. Spread apple filling evenly over the dough. Roll remaining dough to fit the top, either on a well floured pastry board or the back of a sheet pan and then carefully flip it over the top. Press or pinch the edges together, don't worry if it doesn't seal completely, as long as top is completely covering apples. Patch where necessary. Cut several slits in top dough for steam vents.
Bake in 400º oven for 40 minutes, until crust is nicely browned, rotating pan halfway. Remove to rack to cool.
Make glaze. Combine sugar, softened butter, vanilla and milk until smooth, adding more milk if necessary for consistency. Spread glaze over top of crust with an offset spatula and let glaze set and harden. Cut into 2- or 3-inch squares and enjoy!