First mix a marinade for the meat from 1 tablespoon honey, diced onion (approx. 1/4 onion), rosemary, salt, pepper and a little oil and marinate the sliced fillet with it. Possibly add a little more finely chopped lemongrass, but definitely not too much of it.
Let a pan get hot and fry the fillet in it. This creates a lot of liquid, which is removed from the pan with a spoon from time to time and stored. After about 5-10 minutes, the honey from the marinade begins to crystallize, then remove the meat and keep it warm.
Put the remaining onion cubes in the pan with a little oil. Fry until they are translucent. Mix 1/4 liter of water with the broth and add to the onions with the frying juice. Add about 4 tablespoons of honey to the sauce - people tend to underestimate this, and take more than too little honey. Thicken the sauce a little and season with garlic, rosemary, salt and pepper.