For steaks with aioli, lightly pound the steaks and marinate with salt, olive oil, pepper and rum for min. 30 min.
Sear the steaks briefly in a pan in a little olive oil and then cook slowly in the oven at low temperature and 65° C for 2-3 hours.
For the aioli, mix finely chopped bell pepper, onion, parsley, garlic, vinegar and lime juice in a bowl.
Beat egg yolks in a bowl with a mixer, drizzle in oil and mix in until you have a creamy mayonnaise. Mix this with the herb and bell pepper sauce and season with salt and bell pepper.
Dissolve the butter and sauté the red onion in it until translucent, remove from the pan.
Serve the steaks with aioli with the fried onions and with fried potatoes or white bread, as desired.