Set a rack in the lower third of the oven, put a rimmed baking sheet on it and heat the oven to 425°F (220°C).

Combine the flour, baking powder, salt, sugar, egg, shortening and water in a medium bowl.

Beat with an electric mixer on medium speed for about 1 minute, scraping the bowl once, until the batter is smooth with no streaks of shortening or flour. It will be thin and pourable.

Pour the batter into a 9-inch pie pan. It will look thin and pale, which is normal.

Stir the apple pie filling with the lemon juice and cinnamon in a small bowl.

Spoon the filling gently into the center of the batter, leaving about 1 inch (2.5 cm) of batter showing at the edge. Do not stir or spread it.

Set the pan on the hot baking sheet and bake for 45 to 50 minutes, until the crust ring is deep golden and set and the filling bubbles slowly at the center. If the edge browns deeply before 30 minutes, tent the pie loosely with foil.

Check that a thermometer slipped into the thickest part of the crust reads at least 160°F (71°C), and bake 5 minutes longer if it does not.

Cool the pie on a wire rack for 30 to 45 minutes, until the filling stops bubbling and thickens enough to slice cleanly. Serve warm or at room temperature.