Stir together the flour, sugars, cinnamon, and salt in a medium bowl to combine. Add the melted butter and stir until the streusel comes together.
Preheat the oven to 350°F. Spray an 8-inch round cake pan with nonstick cooking spray. Whisk together the flour, baking powder, and salt in a small bowl and set aside.
Beat the eggs, sugar, and olive oil in the bowl of an electric mixer on medium speed for 5 to 6 minutes, until the mixture turns a pale yellow color and forms ribbons when the paddle is lifted. Add the butter, lemon zest, lemon juice, and milk and mix until well combined. With the mixer on low speed, add the flour mixture in three additions, blending until just incorporated.
Press the streusel over the bottom of the prepared pan and pour the batter over the top. Bake for 50 to 55 minutes, until a cake tester comes out clean. Remove from the oven and let cool for 30 minutes. Invert the cake onto a plate and dust with powdered sugar. Serve warm.