Preheat oven to 200°C. Line a baking tray with baking paper.
Sift flour and baking powder into a large bowl. Add salt and butter. Using your fingers, rub the butter into the flour until it resembles fine breadcrumbs. (You can also do this by pulsing briefly in a food processor and then transferring mixture to a large bowl.)
Make a well in the centre of the dry ingredients and pour in the milk. Use a knife to gently mix into a soft dough. Bring together and knead very lightly on a floured surface.
Use a rolling pin to roll dough into a rectangle measuring 20cm x 40cm. Cut in half so you have two squares. Spread each square with basil pesto.
Cut cherry tomatoes in half and pinch gently to squeeze out seeds. Squeeze the tomatoes to remove excess moisture, then roughly chop. Sprinkle on top of the basil pesto along with the crumbled feta.
Roll each square relatively tightly to make a long sausage shape. Seal join by lightly pressing with your fingers so it doesn’t unravel while baking. Using a sharp knife, cut each roll into eight slices to make the pinwheels.
Place on baking tray and bake for 10-12 minutes until lightly golden. Transfer to a cake rack and serve warm, with a spread of butter if you wish.