Step 1

Toss the melted butter, flour, brown sugar, cinnamon, and salt together with a fork until crumbly.

Step 2

Preheat the oven to 425 degrees F and line a muffin pan with papers.

Step 3

Place the flour, sugar, baking powder, and salt in a large bowl and whisk to combine.

Step 4

In a smaller bowl, whisk the melted butter, sour cream, milk, eggs, and vanilla together until smooth.

Step 5

Add the sour cream mixture to the dry ingredients, and fold together until just barely combined.

Step 6

Fill the wells of the muffin pan halfway with the sour cream coffee cake batter, then top with a few teaspoons of the cinnamon crumb topping.

Step 7

Divide the remaining batter equally among all 12 wells of the muffin pan, and top with the remaining cinnamon crumb topping.

Step 8

Bake the crumb cake muffins for 5 minutes at 425 degrees F, then turn the oven temperature down to 350 degrees F and continue to bake for 14 to 18 minutes, or until a toothpick inserted in the thickest part of a muffin comes out clean or with a few moist crumbs.