Preheat oven to 350 degrees Fahrenheit. Grease three (nine-inch) round pans.

In the bowl of an electric mixer, combine all dry ingredients. Add eggs, milk, oil, and vanilla. Dissolve coffee in boiling water. With the mixer running on low, add coffee in a thin stream. Scrape down sides of bowl and mix until combined.

Divide batter among three prepared pans and bake for 30 to 35 minutes, or until a toothpick inserted comes out clean.

Meanwhile, in the bowl of an electric mixer, beat whipped topping until stiff. Add peanut butter and beat until incorporated. Add sugar.

Pulse pretzels in a food processor (you might need to finish them off by smashing them with a rolling pin in a zip-top bag).

In the bowl of an electric mixer, cream margarine for two minutes. Add sugar, one cup at a time. Add smashed pretzels and mix to combine. Add salt and a handful of pretzel chunks.

Once cake is cool, put peanut butter filling in between the layers. Use pretzel buttercream to frost outside of cake.