Preheat the oven to 350°F (177°C). Lightly grease a 10-ounce ramekin with butter.
In a small bowl, stir together the melted butter and sugar.
Add the egg yolk and vanilla, and mix until fully combined.
In a separate bowl, whisk together the flour, cinnamon, baking powder, and salt. Add to the wet ingredients and stir to combine.
Stir in the milk, then gently fold in the blueberries.
Pour the batter into the prepared ramekin.
Bake for 30 to 35 minutes, or until the top is golden and a knife inserted in the center comes out clean.
Optional Glaze: In a small bowl, whisk together powdered sugar, milk or cream, and vanilla until smooth. Drizzle over the cooled cake.Note: If the glaze is too thick, stir in a little more milk or cream. If it’s too thin, add more powdered sugar until it reaches the consistency you like.
Notes
Prep First: Gather all ingredients and read through the steps before starting for a smoother baking experience.
Try Different Berries: Swap blueberries with cherries, raspberries, blackberries, or a mix for a new flavor.
Make It Cinnamon Only: Skip the fruit for a simple cinnamon coffee cake if you prefer a non-fruity version.