Preheat oven to 350° and spray a 9x9 baking pans with non-stick spray.
On the stovetop in a non-stick pan, on low setting, melt chocolate chips & margarine in a saucepan. Stir occasionally until smooth.
In a large bowl, use a whisk to combine 2 kinds of flour, baking powder, cayenne, & salt and set aside for later.
Combine sugar, eggs, & vanilla in your electric mixer’s bowl & beat with the paddle attachment until combined & fluffy, 3-5 minutes.
Gradually add in flour mixture and separate batter into halves, in two bowls.
Combine chocolate mixture with one half of the batter.
Combine pumpkin, oil, cinnamon, & nutmeg with the other half of the batter.
Use a quarter of the chocolate batter to create a layer on the bottom of the pan. Make the next layer with a quarter of the pumpkin batter instead. Smooth with a spatula as necessary.
Repeat the previous 2 steps again, until you have 4 layers. (top-to-bottom: pumpkin / chocolate / pumpkin / chocolate) Use a butter knife or tiny spatula to delicately create the swirl effect between the two batters.
Lay pecan halves, smooth side up, on the surface of the batter in a linear pattern, so each cut square will get at least 1 pecan.
Bake until a toothpick comes out clean, about 45 minutes to 1 hour.
Cool before serving.
Notes
You can also use two 8x8 pans and freeze one for later!