Kati's Cinnamon Roll Cake

My daughter has really taken to cooking and baking. Here is one of my favorites she makes!
Cake -
3 C all purpose flour
1 C sugar
1 T + 1 t baking powder
1 1/2 C milk
2 eggs
2 t vanilla
1/2 C melted butter
Topping -
1 C butter (softened)
1 C dark brown sugar (packed)
2 T flour
2 T cinnamon
Glaze -
2 C powdered sugar
1 T cinnamon
5 T milk
1 t vanilla
For the cake, in a large bowl, mix all ingredients except the butter. Add butter slowly, mixing into cake mixture. Pour into greased 9x13 pan.
For the topping, mix all together until combined. Drop evenly over cake batter and swirl with a knife. Bake @ 350 for 20 - 35 mins until toothpick comes out clean (check cakey part, not topping area). Drizzle glaze over cake while still warm.