Step 1

Preheat oven to 350 degrees Fahrenheit. Spray a 9x9 inch baking dish with non-stick cooking spray.

Step 2

In a medium bowl, whisk together flour, baking powder, salt, and baking soda until combined. Whisk in fresh lemon zest and poppy seeds until lemon zest is incorporated throughout flour mixture. Set aside.

Step 3

In the bowl of stand mixer, or with an electric hand mixer, cream together butter and sugar. Beat in eggs until creamy. Carefully beat in milk, fresh lemon juice, and vanilla extract until combined.

Step 4

Add dry ingredients to wet ingredients, and stir until just combined. Pour batter into prepared baking dish.

Step 5

Stir together oats, all-purpose flour, brown sugar, cinnamon, and salt. Cut in butter until mixture resembles coarse crumbs. Sprinkle over the top of the batter.

Step 6

Bake for 40-50 minutes, or until toothpick inserted in the center comes out with just a few crumbs.

Step 7

Remove to a wire rack to cool. While cake is cooling, stir together confectioner's sugar and one (tablespoon fresh lemon juice until smooth. Add additional lemon juice as needed to reach desired consistency. Drizzle glaze over warm cake. Top with additional lemon zest, if desired.

Step 8

Allow glaze to harden, and serve. Store leftovers in an airtight container.