Preheat the oven to 350°F.
For the topping, mix the flour, brown sugar, salt, and cinnamon in a bowl. Add the butter and use your fingertips to combine until the mixture is crumbly. Refrigerate while preparing the batter to keep it nice and crumbly.
1 cup all-purpose flour, 1/2 cup packed dark brown sugar, 1-1/2 tsps ground cinnamon, pinch of table salt, 6 tbsps unsalted butter, cold, cut into pieces
Butter and flour a 9x13 cake pan, or simply spray it with cooking spray.
In a small bowl, whisk together the flour, baking powder, baking soda, salt, and spices.
2 cups all-purpose flour, 1-1/2 tsps baking powder, 1/2 tsp baking soda, 1 tbsp ground cinnamon, 2 tsps ground ginger, 1/2 tsp ground nutmeg, 1/4 tsp table salt
In a large bowl, whisk together the oil, applesauce, pumpkin, vanilla, and both sugars until fully combined. Whisk in the eggs, then gently stir in the flour mixture until just combined—be careful not to overmix.
1/3 cup vegetable oil, 3/4 cup unsweetened applesauce, 1 (15 oz) can pumpkin puree, 1 tsp vanilla extract, 1-1/2 cups granulated sugar, 1/2 cup packed dark brown sugar, 2 large eggs, room temperature, lightly beaten
Pour the batter into the prepared cake pan and spread it out evenly. Sprinkle the reserved topping over the batter. Bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan on a wire rack for at least 20 minutes before serving.