Made this tasty dish a few nights ago. It was very light tasting and yet satisfying.
We roasted the thinly sliced fennel and onions with a touch of olive oil in the oven at 425 deg F until they started to soften and caramelize, about 15 minutes, stirring at least once.
Meanwhile we brought some home-grown, oven-roasted tomatoes (previously slow-roasted at 275 deg F for 3 hours with whole garlic cloves, a hint of thyme, salt and pepper) up to serving temperature in an oven proof skillet. We added the onion/fennel mixture to the pan reserving about 1 cup for later. We did not mix the onion mixture with the tomatoes, just let it fall into the tomatoes.
We then high heat seared the skin-on Red Snapper fillets in a non-stick skillet with olive oil and then placed them on top of the tomato/fennel and onions and topped with the remaining onion/fennel mixture. The entire pan was then returned to the 425 deg F oven to finish cooking the red snapper through and to give additional browning to the veggies.