Mexican Chocolate Cupcakes with a dulce de leche buttercream have a kick of spice of cayenne pepper with a buttercream sweetened with dulce de leche cream.
Add the first six cake ingredients together in a large mixing bowl. Beat with an electric mixer on low to medium speed until moistened, about 30 seconds. Add eggs one at a time, until the batter is well-mixed. Increase speed to high and beat until thick, 2 minutes longer.
Cream butter in an electric mixer on medium-speed until smooth and fluffy, about 2-3 minutes. Then add dulce de leche, vanilla and cinnamon and mix on low-speed until combined. Gradually add in the milk and powdered sugar, alternately, until combined. Then beat on medium speed until light and fluffy, another 3-5 minutes. (Add in more powdered sugar if consistency is too thin.)