Brush the potato wedges with olive oil and bake for 20-30 minutes on a baking sheet until tender and browned.
Turn if necessary during cooking.
At the same time as the potato is cooking, put the pepper halves cut-side down on a tray and roast for 15-20 minutes until tender and slightly charred.
You can peel them if you prefer although it is not strictly necessary.
Whizz the peppers, beans, lemon juice and ketchup in a food processor until you have a thick puree.