Make the marinade: Heat the olive oil in a small saucepan over medium heat. Sauté the onion with a pinch of salt for 5 minutes until softened. Add the garlic and cook for 1 minute more.
Simmer: Add the smoked paprika, tomato puree, maple syrup, Worcestershire sauce, balsamic vinegar and soy sauce. Stir well and simmer gently for 5-6 minutes. Taste and adjust the seasoning, adding more soy for a more savoury flavour. Leave to cool.
Marinate: Pour the cooled marinade over the steaks in a dish. Cover with cling film and refrigerate for at least 1 hour, or up to 2 days.
Cook the steaks: Remove from the fridge 30 minutes before cooking. Heat a griddle pan or frying pan until smoking hot. Scrape off excess marinade. Cook for 3-4 minutes per side for medium-rare.
Rest and serve: Rest for 5 minutes, then slice against the grain and serve.
