Cake: Grease and flour a 9“ x 9“ pan. Preheat oven to 400F.
In a large bowl, sift flour, baking powder, salt, and sugar together. With a fork, cut in butter.
In a separate bowl mix egg with milk. Add to flour mixture and stir until well blended and smooth. Scrape into prepared pan and spread evenly.
Brush top with melted butter. Sprinkle on Pretzel Streusel topping (below) and bake for 25 to 30 minutes.
Combine ingredients. Sprinkle over top of unbaked coffee cake. Bake according to directions above.