Chilli cheese hot dogs

Ingredients

• 60 millilitre olive oil
• 1 medium red onion, finely chopped
• 400 gram good-quality lean beef mince
• 200 millilitre ketchup, plus extra to serve
• 1 tablespoon chilli flakes (or to taste)
• 1 tablespoon smoked paprika
• 1 tablespoon american mustard, plus extra to serve
• 1/4 white cabbage, finely shredded
• 1/2 lemon, juice only
• 4 soft hot dog rolls, split lengthways
• 4 large good-quality frankfurters
• 1 cup grated aged cheddar