I found this recipe on YouTube.

Streusel: 

Flour  45 g

Sugar 65g

Cinnamon 1/2 tsp

Mix them well. Cut into butter around 50g. And make them into crumbs.
Cake:

60g butter stir till smooth.

Add in 100g white sugar and stir till fluffy.

Beat in 1 large egg & 1/2 tsp vanilla.

Mix them well.
Prepare:

130g flour, 1 tsp baking powder, 1 tsp salt. Mix them well.

80ml milk.
1. First add 1/3 flour part into butter mixture. Then add 1/2 milk. Mix them well.

2. Add another 1/3 flour & rest milk. Mix well.

3. Add the rest flour. Mix well.

4. Put batter into the pan evenly.

5. Spread blueberries (video says 2 cups blueberries, but I didn’t have that much) on the batter.

6. Sprinkle crumbs evenly on the top.

7. Preheat oven to 180 degree C and bake for 40-50 mins. ( I baked 40 mins. You can test with a toothpick).

My husband loves it.