Position a rack in the center of the oven and preheat to 375 F. Lightly butter a 10-inch tart or quiche pan.
Whisk together the flour, baking powder, and salt in a bowl. Mix in the rolled oats, sugar or Sucanat, and almonds. Cut the butter in using a pastry cutter or your fingers, until the butter is mixed in and the mixture looks crumbly. Whisk the egg and water together and stir it in with a fork or a wooden spoon-The tart dough should pull together somewhat but still be crumbly or chunky.
Mix the apples, jam and lemon zest and juice in a small bowl. Set aside.
Press two-thirds of the dough evenly over the bottom of the prepared pan, pressing all the way up the sides and leveling off at the top. Spoon the prepared fruit filling evenly into the crust, and crumble the remaining dough evenly over the top.
Place a layer of aluminum foil on the shelf below the tart pan, in case the filing bubbles over. Place tart in oven and bake at 375 F for 10 minutes, then, without opening the door, reduce heat to 350 for another 35 to 45 minutes. Tart is done when crust is golden to dark brown and jam filling is bubbly.
Cool on a wire rack for 20 minutes and serve.