Prep Pan and Oven: Line the cake pan with parchment paper. Preheat oven to 360°F (180°C).
Mix Wet Ingredients: In a mixing bowl, whisk together the almond milk, olive oil, 3/4 cup sugar, vanilla extract, and optional lemon zest until well combined.
Sift Dry Ingredients: Sift in the all-purpose flour, baking powder, and salt through a fine-mesh sieve.
Finish Batter: Whisk or mix with a hand mixer for a few seconds until you have a smooth and thick cake batter. Do not over-mix.
Add Filling Apples: Core and remove the seeds from 2 1/2 apples (keep the peel on). Cut into small pieces and fold them into the batter with a spatula.
Pour Batter: Pour the batter into the prepared cake pan.
Top with Apples: Slice the remaining 1 1/2 apples thinly (cored/seeded) and arrange them in a circular, overlapping pattern over the top of the batter.
Apply Topping: In a small bowl, mix the 2 tablespoons of sugar with the 1 teaspoon of cinnamon. Sprinkle this mixture evenly over the apple slices on top of the cake.
Bake: Bake on the center rack for 55 minutes to 1 hour. A skewer inserted in the center should come out mostly dry. If not, continue baking in 5-minute increments.
Cool: Take the cake out of the oven and let it cool for 15 minutes before removing it from the pan. Cool for at least 1 hour before slicing.