Preheat Oven to 350

Mix first 5 ingredients until combined.

Add cake mix and baking soda. Mix until combined.

Grease 9 x 13 pan and add batter.

Mix brown sugar, 1/2 c four, melted butter. Mix and sprinkle over cake

Bake for 25 to 30 minutes

In sauce pan mix 1/2 cup brown sugar, sugar, 1 tsp vanilla and heavy cream. Bring to a simmer, remove from heat. Stir until sugar is melted.

Poke holes in warm cake and pour topping over cake.