Prep the pan and oven: Preheat the oven to 350°F (175°C).
Generously grease a 10–12 cup bundt pan with butter and dust with flour, or use baking spray with flour. Make sure every curve is coated to prevent sticking.
Season the apples: In a bowl, toss the chopped apples with granulated sugar, cinnamon, and lemon juice. Set aside while you make the batter.
Make the ripple mixture: Stir together brown sugar, cinnamon, flour, and a pinch of salt.
This will create that apple fritter-like streak through the cake.
Combine dry ingredients: In a large bowl, whisk flour, baking powder, baking soda, and salt. Set aside.
Mix the wet ingredients: In another large bowl, whisk granulated sugar, brown sugar, oil, and melted butter until smooth. Whisk in eggs one at a time.
Add sour cream and vanilla, then whisk until creamy.
Bring the batter together: Add half the dry ingredients to the wet mixture and mix gently. Stir in the milk. Add the remaining dry ingredients and mix just until combined.
Do not overmix.
Layer the cake: Spoon about one-third of the batter into the prepared bundt pan and spread evenly. Sprinkle one-third of the ripple mixture over the batter. Scatter one-third of the apples on top.
Repeat two more times, ending with apples on top. Lightly press the top apples into the batter.
Bake: Bake for 55–65 minutes, or until a toothpick inserted near the center comes out clean or with a few moist crumbs. If the top browns too quickly, tent loosely with foil for the last 10–15 minutes.
Cool and unmold: Let the cake cool in the pan on a rack for 15–20 minutes.
Run a thin spatula around the edges and center tube, then invert onto a wire rack. Let cool completely before glazing.
Glaze: Whisk powdered sugar, milk, vanilla, and a pinch of salt until smooth and pourable. Drizzle over the cooled cake, letting it run down the sides.
Let the glaze set for 15–20 minutes before slicing.