Preheat your oven to 200°C (180°C fan/400°F/gas 6).
Place paper muffin cases in each hollow of the muffin tin.
Gently warm the butter in a small pan over low heat until it melts, then let it cool.
In a large bowl, combine the flour, baking powder, ground almonds, cinnamon, and sugar.
In a medium bowl, beat the eggs and mix in the yogurt, milk, and cooled melted butter.
Combine this mixture with the dry ingredients.
Add the raspberries and apple and briefly stir to incorporate. (Refer to "Make a light mixture" below.)
Scoop the mixture into the muffin cases. Bake for roughly 25 minutes or until the muffins have risen well and feel firm to the touch.
Meanwhile, prepare the glaze: gently heat the sugar and orange juice in a small pan until the sugar dissolves. Increase the heat slightly and let the mixture bubble for about 30 seconds until it forms a slightly syrupy consistency—avoid overcooking.
Once the muffins are out of the oven, let them rest in the tin for 1-2 minutes before transferring them to a wire rack. While they're still warm, brush the top of each muffin with the glaze. Allow the muffins to cool.