Preheat the oven to 350° F. Spray the bottoms and sides of a 9-inch x 13-inch baking dish with nonstick spray.
In a large bowl, whisk together the flour, cocoa powder, baking powder, instant espresso and salt. Set aside.
Cream together the butter and granulated sugar for about 5 minutes, until the mixture is light yellow and fluffy. Mix in 3 teaspoons of the vanilla extract. Add in only 4 of the eggs, beating the mixture after each egg is added. With the mixer running on low, slowly add in the dry mixture. Beat the dry and wet ingredients - scrape down the bowl once or twice during this - until everything is just combined.
In a separate medium-sized bowl beat together the remaining teaspoon of vanilla, the remaining egg, the cream cheese, confectioner's sugar and cayenne pepper. The mixture should be thoroughly combined and smooth.
Pour half of the chocolate batter into the prepared baking pan and spread it to cover the bottom of the pan. Spoon all of the cream cheese mixture over this, and then top this layer with the rest of the chocolate batter. Pull a rubber spatula through the layers to create swirls of cream cheese batter in the chocolate. Place the pan in the oven and bake for 40-44 minutes. It should be baked through but a tester inserted into the center should come out with a little batter on it - do not overbake the brownies or they will be very dry.
Place the pan on a cooling rack and let the brownies cool for about 30 minutes before slicing.
Brownies can be stored tightly wrapped for up to three days. Makes 24 brownies.