Pre-heat oven to 220ºC (fan) ready for your fish.
First make the salsa. Put the onion in small bowl, squeeze over the lime juice and add a pinch of salt, mix well and leave the onions to marinade in the lime for at least 10 minutes. Then add the chopped kumquats, capers, honey, olive oil, mint along with some salt and pepper. Taste and add more lime or salt if it needs a boost. Set aside.
Next prep your fish. Slash the fish skin 3 or 4 times, then rub the skin with olive oil, garlic (going into the slashes) and season with salt and pepper. Leave sit for 10 minutes.
Place some lemon slices in the fish cavity, and a few on the bottom of your parchment lined or ceramic baking dish. Add the fish on top and then bake for 12-14 minutes, turning over half way. The fish skin should flake easily when done. If your fish is smaller, cook for less time or particularly large, a bit longer.
Serve with the kumquat salsa scattered over the top, and roasted potatoes and green salad for a simple accompaniment.