Preheat oven to 350 F (175 C)
Grease a 9-inch (22 cm) pan with a bit of olive oil and sprinkle bit of flour.
Make the crumble: In a small bowl place the breadcrumbs and sugar and add olive oil gradually (do not add all of it at once) while pressing the mixture with a fork, until you have a crumbly texture and all the breadcrumbs are wet. Set aside.
In a medium bowl mix the dry ingredients (flour, baking powder and cinnamon) and set aside.
In a larger bowl, mix the olive oil with the sugar until smooth and then add the eggs one by one, vanilla and milk. Mix well. I used a whisk and mixed by hand.
Add the flour mixture to the wet mixture gradually mixing until combined.
Add the sliced apples and toss until they are coated with the batter and set aside.
Empty the mixture in the prepared pan and bake for 45 minutes. Remove from oven and sprinkle over the cake the crumble, bake for another 10-15 minutes until crumble is golden.
Cool for at least 30 minutes. Slice and serve as is or with a dollop of Greek yogurt.