Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4 and grease a 12 hole donut tins (or two 6 hole ones) with the butter
In a mixing bowl stir together the self raising flour and caster sugar. Add in the lemon zest and mix in
In another mixing bowl or a jug, whisk together the milk, eggs and vegetable oil. Pour into the flour mixture and stir together until a smooth batter forms
Divide the batter between the tins. You can put the batter into a piping bag to make it a bit neater to dispense into the trays, but you can do it with a spoon too, or pour into a jug
Bake them for 12 minutes or until they spring back when you press your finger into them, then remove them from the tin (I use a spoon to gently prise them out) and leave to cool on a rack
Make the white icing by mixing the ingredients together
Spread the icing on top of the donuts with a piping bag or spoon
Make the yellow icing by mixing the ingredients together, put into a piping bag and drizzle it over the donuts. Add some sprinkles if you like
They are best the day they're made, but you can store leftovers in an airtight container and eat within 3 days
Video
Notes
Make sure your ingredients, particularly the eggs, are at room temperature before you start baking.
You can use a different type of oil besides vegetable oil. I'd recommend one that doesn't have a strong flavour, canola and sunflower oil would both work well.
You will need a 12 hole donut tin (or two 6 hole donut tins) to make this recipe.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.