01 -
Preheat oven to 375°F. Grease or line 9x9 baking dish with parchment paper.
02 -
Beat egg, then mix in sugar, milk, salt, oil, and vanilla. Spoon flour on top, add baking powder, gently combine, then mix into batter.
03 -
Melt butter and mix with brown sugar, cinnamon, flour, and optional nuts until well combined.
04 -
Pour batter into pan. Sprinkle with streusel and poke 12-18 times halfway into batter.
05 -
Bake 25-30 minutes until toothpick comes out with moist crumbs. Don't overbake.
06 -
Mix butter and powdered sugar. Thin with milk to desired consistency and drizzle over cake.