Grease a 22 cm springform pan with butter, line base with baking paper.
Rinse blueberries, shake off excess water (but don’t pat dry). Set aside about 1/3 of the blueberries (for topping cake). Toss remaining blueberries in flour, set aside.
Whisk Wet in a large bowl. Add flour and salt, sprinkle over baking powder.
Whisk until just combined – few small lumps is fine. Stir through blueberries (including loose flour in bowl). Pour into pan, top with remaining blueberries.
Place in oven, TURN DOWN to 180C (standard) or 160C (fan/convection). Bake 50 minutes or until skewer comes out clean. Remove sides of springform pan and cool on a rack, then once cool remove the base.
Sprinkle with icing sugar (powdered sugar). Serve!