To make the streusel, line a quarter baking sheet with parchment paper. In a small bowl, whisk together flour, sugar and cinnamon until combined. Using your fingers, rub in room temperature butter until incorporated and large clumps form when you press the mixture together. Spread onto prepared baking sheet and refrigerate for 20 minutes or freeze for 10 minutes.

Preheat oven to 350°F. Grease an 8 x 8 metal baking pan and line with parchment paper, letting the paper overhang the edges for easy removal.

In a large bowl, whisk together flour, cinnamon, baking powder, baking soda and salt.

In another large bowl, stir together oil and the sugars. Whisk in the eggs until combined, then stir in the yogurt and vanilla.

Using a rubber spatula, fold the dry ingredients into the wet ingredients just until combined. Pour into prepared pan and sprinkle evenly with chilled streusel.

Bake for 45-55 minutes, or until the top is light golden brown, the center is firm when lightly touched, and a toothpick inserted in the center comes out clean.