Spelt Blueberry Muffins

Name: Spelt Blueberry Muffins
Cuisine: American
Ingredients: 275g (2¼ cups) spelt flour (see note 1); ½ tsp baking powder; ½ tsp salt; ½ tsp cinnamon; pinch of nutmeg; 115g (1 cup + 1 tbsp) sugar; 175g (¾ cup) butter (chopped into pieces); 2 small eggs (weighing 100g in total); ½ tsp vanilla; 100ml (¼ cup + 1 tbsp) milk; 150g (1 cup) fresh blueberries; brown sugar (for sprinkling)