Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan with nonstick spray and parchment paper.

In a small bowl, combine 1/4 cup light brown sugar, 1 tablespoon flour, and 1 teaspoon ground cinnamon. Set aside.

In a medium bowl, mix 1/2 cup flour, 1/2 cup light brown sugar, and 1 teaspoon cinnamon. Add 1/4 cup cold diced unsalted butter and mix until crumbly.

In a separate bowl, whisk together 1 1/2 cups all-purpose flour, 2 teaspoons baking powder, and 1/2 teaspoon salt. Set aside.

In a large bowl, mix 1/2 cup granulated sugar, 1/2 cup light brown sugar, 1 cup applesauce, 1/2 cup plain Greek yogurt, 1/4 cup vegetable oil, 2 eggs, and 1 teaspoon vanilla until smooth.

Gently fold the dry ingredients into the wet mixture until just combined; avoid overmixing.

Pour half of the batter into the prepared pan, then sprinkle with the cinnamon sugar mixture. Top with the remaining batter and smooth it out.

Sprinkle the streusel topping evenly over the batter.

Bake in the preheated oven for 40-50 minutes until golden brown and a toothpick inserted comes out clean.

Cool in the pan for 10-15 minutes before lifting out and transferring to a wire rack to cool completely. Slice and serve.