Preheat your oven to 350℉ (175℃) and prepare an 8x8 baking dish with parchment paper.

In a mixing bowl, combine 2 beaten eggs, ½ cup melted butter, and 1 cup of mashed sweet potato until smooth. Add ½ cup of granulated sugar and 1 teaspoon of vanilla extract, stirring until well incorporated.

In a separate bowl, whisk together 1 ½ cups of all-purpose flour, 1 teaspoon of baking powder, ½ teaspoon of baking soda, ½ teaspoon of salt, and 1 teaspoon of cinnamon.

Gently fold the dry mixture into the wet mixture, stirring until just combined.

Pour half of the batter into the prepared baking dish and spread evenly with a spatula.

In a small bowl, cut together ¼ cup of cold butter with ½ cup of light brown sugar and ⅓ cup of flour until the mixture resembles coarse crumbs.

Sprinkle half of the crumble mixture over the first layer of batter, then pour the remaining batter over the crumble before adding the last layer of crumble on top.

Bake for 35-40 minutes, until a toothpick comes out clean or with a few moist crumbs.

Let the cake cool in the pan for about 10 minutes. If desired, prepare a glaze by mixing powdered sugar with a splash of milk, then drizzle it over the cooled cake.