Preheat your oven to 350°F. Grease an 8×8-inch baking pan and tell yourself you’ll wash it immediately after baking (you won’t, but the optimism matters).

In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.

In another bowl, mix the sour cream, melted butter, eggs, and vanilla until smooth and creamy.

Stir the wet ingredients into the dry ingredients just until combined. Do not overmix—we want tender coffee cake, not emotional resilience training.

In a small bowl, mix together the brown sugar, cinnamon, and melted butter for the swirl.

Spread half of the batter into the prepared pan. Sprinkle half of the cinnamon mixture evenly over the batter.

Spoon the remaining batter on top (don’t worry about perfection—this is a cozy bake, not a Pinterest competition). Sprinkle the rest of the cinnamon sugar over the top.

Use a knife to gently swirl everything together. You’re aiming for “effortlessly rustic,” not “chaotic gremlin energy.”

Bake for 35–40 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs.

Let cool slightly. If glazing, whisk together glaze ingredients and drizzle generously over the top while still warm.