Preheat oven to 350 degrees and spray a 9x13 baking dish with pam baking spray, set aside
Using a large bowl, whisk together the flour, sugar, salt, baking powder, nutmeg and cinnamon until combined
Mix in the eggs, pumpkin and vanilla until combined and smooth
Mix in the melted butter
Spread batter into the baking dish and set aside
Using a medium bowl, whisk together the filling ingredients until combined
Drop in spoonfuls the filling into the batter
Swirl into the batter using a butterknife
Place into the oven and bake for 30-40 minutes or until a toothpick comes out clean
Allow to sit and cool on the counter for a few minutes while you make the frosting
Using a medium bowl, whisk together the ingredients for the frosting until combined and smooth
Pour over the cake
Cut and serve!