Peel and chop the onion. Clean the chillies, cut lengthwise, remove seeds, wash and chop finely.
Heat the oil. Brown the onion cubes in it for about 5 minutes. Add chilli. Deglaze with orange juice, bring to the boil and boil down on approx. 1⁄4. Add tomatoes and simmer for about 5 minutes while stirring. Stir in maple syrup and mustard. Season to taste with salt.