Remove the skin then chop the grilled pepper and onion into tiny bits or very thin slices.
Sift the flour, baking powder and salt into a mixing bowl.
Add the margarine pieces and rub with your fingers until the mixture resembles breadcrumbs.
Add the onion and red pepper pieces, together with the chopped rosemary and freshly ground peppercorn. Mix with a palette knife to a soft dough, gradually adding the milk and the cheese (if used).
You might need to add more milk (the dough should be thick, binding well together).
Make a ball shape and rest in the fridge for an hour or in the freezer for 15 minutes.
Heat the oven to 180°C.
Line a baking sheet with parchment paper.
Roll the dough out on a board dusted with gluten-free flour to about 1 cm thickness and stamp out scones using a cutter or small cup.
Place them on the prepared baking sheet and bake for 10-15 minutes until risen and golden.
Cool them on a wire rack, then serve.