Preheat your oven to 180°C (350°F). Grease your baking pan lightly with butter. You can also line it with parchment paper. This helps the cake come out easily after baking.

Take a bowl and add flour, baking powder, and salt. Mix them well using a spoon or whisk. This step helps everything combine evenly later.

In another bowl, beat butter and sugar until light and fluffy. This takes about 3–4 minutes. It makes the cake soft and airy.

Add eggs one at a time. Mix well after each egg. Then add vanilla extract. This gives the cake a sweet and warm flavor.

Now slowly add the dry ingredients into the butter mixture. Add milk little by little. Mix gently until smooth. Do not overmix.

Add fresh blueberries into the batter. Gently fold them using a spatula. This keeps them whole and juicy.

In a small bowl, mix brown sugar, flour, and cinnamon. Add cold butter cubes. Use your fingers to make a crumb texture.

Pour the batter into the prepared pan. Spread it evenly. Sprinkle the crumb topping on top.

Place the pan in the oven. Bake for 40–45 minutes. The top should be golden brown. Insert a toothpick to check. It should come out clean.

Let the cake cool for 15 minutes. Then slice and serve. It tastes amazing warm or at room temperature.