Preheat oven: Set oven to 350°F (175°C) and line a muffin pan with cupcake liners.
Make the batter: In one bowl, mix flour, baking powder, cinnamon, and salt. In another bowl, cream butter and sugar until fluffy. Beat in eggs and vanilla, then alternate adding dry ingredients and milk until smooth.
Cook the apple filling: In a small pan, melt butter and add apples, brown sugar, cinnamon, and lemon juice. Cook 5 minutes until soft and syrupy.
Make the crumb topping: Mix flour, brown sugar, and cold butter using a fork or your fingers until crumbly.
Assemble: Fill liners two-thirds full with batter. Spoon apple filling on top and sprinkle with crumb mixture.
Bake: Bake 18–20 minutes or until a toothpick inserted comes out clean.
Cool & serve: Let cool before topping with caramel drizzle or powdered sugar.