Preheat the oven to 375 degrees F. Line 18 muffin cups with cupcake liners.
For the cupcakes: Combine the cake mix, eggs, water, oil and marsala in a large bowl. Using a hand held mixer, beat on medium speed until combined, about 2 minutes. Fill each muffin cup 3/4 of the way to the top (about 3 tablespoons). Bake until golden brown and a toothpick inserted in the center comes out clean, 15 to 20 minutes. Remove to a wire rack to cool.
For the frosting: While the cupcakes are cooling, combine the mascarpone, cream cheese, espresso powder, sugar and salt in a medium bowl. Using a handheld mixer, beat on medium speed until light and fluffy, about 1 minute. Divide the frosting evenly on the cupcakes and spread over the tops. Dust with cocoa powder and serve. Store in the refrigerator.