Chop rhubarb stems into 5mm to 10mm chunks, place in a pan with 5 to 10mm of water and heat until the water is just boiling such that the rhubarb is softened ? do not let the rhubarb disintegrate.
Mix flour, baking powder, sugar, almond extract, egg, melter butter and milk in a mixing bowl using the back of a spoon until you get a smooth mixture.
Using two teaspoons, spoon a small dollop of the muffin mixture into each case such that the bottom of each case is just covered. Spoon the rhubarb chunks on top of the muffin mix trying to keep the rhubarb mostly towards the centre of the muffin case. Spoon the rest of the muffin mix on top of the rhubarb. Do not worry too much about smoothing the mixture out as it will spread in the oven. Sprinkle the tops of the muffins with almond flakes
Place in the centre of a preheated oven at 200°C for 20 minutes (in an electric fan oven, adjust times for your oven) until golden brown.