Preheat your fan-assisted oven to 180°C (365°F). Grease a baking tray lightly with oil and line it with parchment paper to prevent sticking.
In a mixing bowl, cream the butter and sugar together on high speed until the mixture is pale and fluffy. Reduce the speed to medium and add the eggs one at a time, making sure each is fully incorporated before adding the next. Add the vanilla bean paste and mix until combined.
Add the sifted flour, baking powder, and salt to the wet mixture. Mix on low speed until fully incorporated. If the batter seems too thick, add two tablespoons of milk or water to reach the desired consistency.
Transfer the batter to the prepared baking tray, spreading it evenly. Arrange the fresh fruit on top—halve the strawberries, chop the rhubarb into chunks, and quarter the apricots.
In a separate bowl, combine the crumble ingredients. Rub the mixture between your fingers until it forms coarse crumbs. Sprinkle the crumble evenly over the fruit-topped cake.
Place the baking tray in the middle shelf of the preheated oven. Bake for 40-45 minutes, or until a toothpick inserted into the center of the cake comes out clean or with just a few moist crumbs.
Allow the cake to cool in the tray for 10 minutes before serving. For quicker cooling, transfer the cake to a cooling rack with the help of another person. Slice and enjoy with a cup of coffee or tea. Smacznego!