Since this recipe mentions ingredients for 4 portions, for 1 portion, the ingredients would only be 1/4 of the 4 portions ingredients.
So we have to divide everything by 4
So onions = 200/4 = 50 g
Carrots = 160/4 = 40 g
Oil = 3/4 = 3/4 tbsps = 0.75 tbsps
Tomatoes = 600/4 = 150 g
Vegetable stock = 1.2 / 4 = 0.3 L