Preheat oven to 350°F.
Spray two 9x3-inch round cake pans with flour-based baking spray and line bottoms of pans with parchment. In a medium saucepan, stir together brown sugar, butter and 3 tablespoons cream over low heat until melted, about 5 minutes. Pour brown sugar mixture into prepared pans, dividing equally. Divide 1 cup of chopped pecans between the pans, sprinkling evenly.
Beat eggs, sugar and oil in bowl of an electric mixer until well blended; stir in pumpkin and 1/2 teaspoon vanilla extract. Whisk together flour, baking powder, baking soda, pumpkin pie spice and salt in a separate bowl. Add dry ingredients to pumpkin mixture and stir until incorporated. Pour half of the batter into each pan and smooth tops using a rubber spatula.
Bake 30 to 35 minutes, until a toothpick inserted in center of cakes comes out clean. Let cool in pans about five minutes, then invert out onto racks and remove paper. Let cool completely.
Beat remaining 1 3/4 cups cream in a large bowl with mixer on high speed until soft peaks form. Gradually add in powdered sugar and remaining vanilla extract. Set one cake layer on a serving plate, pecan praline side up. Spread two-thirds of whipped cream mixture over top, and add second cake layer with praline side up. Top with remaining whipped cream mixture and sprinkle with remaining pecans.
This cake can be served at room temperature, but it’s also very tasty when served chilled!