Preheat the oven to gas 4, 180°C, fan 160°C. Grease and line a shallow 25 x 15cm (10 x 6in) baking tin.
Sieve the flour, baking powder and cinnamon into a bowl and set aside.
Using a metal spoon, beat the butter and sugar in a mixing bowl until light and fluffy. Stir in 2tbsp of the flour mixture (this will prevent it curdling), then crack in the eggs, one at a time. Stir to combine.
Gradually add the remaining flour mix, yogurt and vanilla, then stir in the apple, oats and blueberries.
Spoon the mix into the tin and smooth the surface. Scatter over the raspberries, gently pressing them into the mix. Bake for 20 minutes, cover with foil, and bake for a further 25–30 minutes. Cool in the tin before slicing.