The BEST moist coffee cake recipe that is easy to make 5 minutes prep time with just a few staple ingredients.
Preheat oven to 375°.
Beat egg in mixing bowl. Mix in sugar, milk, salt, oil, and vanilla.
Spoon flour into measuring cup. Dump flour on top of the batter. Sprinkle baking pwder over flour and gently mix into the top half of the flour. Stir flour mixture into batter until combined. Pour into greased, or parchment lined, 9x9 baking dish.
In a microwave-safe bowl, melt butter in microwave. Remove and mix in brown sugar, cinnamon, and flour and stir until well combined. Add nuts if desired.
Sprinkle streusel onto the cake.Use a finger or the small end of a wooden spoon to poke the streusel halfway down into the cake batter, randomly 12-18 times.
Bake for 25-30 minutes, until a toothpick inserted in the middle comes out with moist crumbs (not runny batter). Do not overbake or it will be more dry!
(optional step) Mix butter and powdered sugar. Thin with milk until desired consistency. Lightly drizzle cake with icing.
Note: Spoon flour into the measuring cup for the cake batter. For the flour in the topping, I just scoop it straight with the measuring spoon.
Tip: Do not over-bake or it will dry out the cake.