• Butter and flour a 10 inch spring-form pan. preheat the oven to 360º

The Filling and Topping

• Place all of the topping ingredients in a medium bowl, and use a pastry cutter, or just your fingers, to mix everything together really well. The mixture will be crumbly with big lumps. Set aside.

The Cake

• Measure the flour, baking powder, salt and spices in a medium mixing bowl, and whisk together until thoroughly combined, and set aside.
• In a large mixing bowl, whisk the eggs and brown sugar, until smooth.
• Whisk in the butter, the vanilla, then the yogurt, and then finally the pumpkin.
• Empty the flour mixture into the wet ingredients, and fold together with a rubber scraper, or a large wooden spoon, until completely combined. You don't want any dry spots of flour.
• Scrape half of the batter into the prepared pan, and level out.
• Sprinkle half of the filling and topping mixture even over the batter.
• Scrape the remaining batter over the filling, and careful level it, take care not to disturb the filling too much.
• Sprinkle the remaining topping evenly on the batter.
• Bake in the preheated oven for about 60 to 65 minutes, turning twice to ensure even baking. Check for done-ness after 55 minutes - a toothpick or skewer inserted near the center, should have no more than a few moist crumbs on it.
• When the cake tests done, remove it to a wire rack, and cool for 5 minutes.
• If using a springform pan, carefully run an offset spatula, or butter knife around the edge of the pan to loosen the cake. Carefully remove the ring from the pan, and continue to cool the cake on the rack. For other types of pans, allow to cool about 15 minutes before loosening sides with a butter knife, and removing to a cooling rack. If you have to turn the cake upside-down to get it out of the pan, some of the topping may fall off, but just sprinkle it back over the top.
• Serve slightly warm, or at room temperature. You can have it with whipped, lightly sweetened cream, vanilla ice cream, butter, or just plain.
• Leftovers can be kept at room temperature for several days, but the cake should refrigerated for longer storage than that. Can be frozen.