Method:

Place your watermelon and banana in the freezer to freeze for 6 hours or overnight.
Add your frozen fruit to a blender adding t1 teaspoon of vanilla and lemon juice, depending on the size of your blender you might need to do this in 2 batches.

Blend until the mixture resembles a frozen smoothie. Add your cream to a mixing bowl along with your icing sugar and remaining vanilla, whip until soft peaks form.

Add some of the frozen watermelon mixture to a serving glass and top with the whipped cream, serve with steak.