In a large bowl on low speed beat the oil, eggs, sugar, pumpkin, spices, salt, and baking powder together until smooth 1 - 2 minutes. Don't over mix.
Stir in the flour by hand until just combined.
Spoon half the batter into the pan (13 + 1/2 ounces, if you want to weigh it) and spread it out evenly.
Sprinkle the filling evenly over it and then spoon the rest of the batter over the filling smoothing it out from edge to edge.
Crumble the topping over it from edge to edge.
Bake 40 - 45 minutes until a toothpick from the center comes out with no wet batter on it, dry crumbs are OK.
Cool on a wire rack.
Whisk the confectioners' and milk together to make a glaze. If it seems too thick add a tiny bit more heavy cream. Drizzle over top of the cake.
If you used parchment paper you can remove the cake to a cutting board or platter to cut into squares and serve. If you buttered the pan cut and serve right out of the pan.
Store leftovers tightly covered in a cool, dry place 4 - 5 days.