Preheat your oven to 375F (190C). Generously rub the sides and bottom of an 8-inch square pan with butter. Add a bit of flour, and tip the pan from side to side until it’s well coated with the flour. Tap the pan to remove any excess.
Prepare the crumb topping first. Add the flour, sugars, salt, and cinnamon to a deep bowl; whisk to combine. Using a fork, stir in the melted butter, making sure there are no dry bits of flour.
To make the muffin batter, add the flour, sugar, salt, and baking powder to a clean deep bowl.
In a small bowl or large measuring cup, combine the buttermilk, egg, and melted butter. Beat with a fork. Pour the buttermilk mixture over the flour mixture. Stir with a fork until just combined. Using a rubber spatula, fold in the cherries.
Evenly spoon into the prepared muffin tin. Evenly sprinkle the crumb topping onto the muffins, pressing it in gently so it sticks.
Bake until a deep golden brown, and until a metal skewer inserted in the center comes out clean, about 35 minutes. Remove from the oven. Set the tray on a wire rack, and allow muffins to cool at least 30 minutes before serving.
Make Ahead
Once baked, let cake cool completely. Cut it into pieces, and wrap them individually in plastic film. Store in a tightly sealed ziptop bag. Take pieces out the night before you plan to eat them, and let them thaw in the fridge overnight.
Make It Your Own
This is basically my master recipe for muffins, which I’ve adapted for a square pan. Taking it one step further, the fruit changes with the seasons. Raspberries, blackberries, and diced peaches are a few of my other favorites during summer months. You can also play around with the spice in the crumb topping. Swap out the cinnamon for allspice, cloves, or ground ginger.