Preheat the oven to 250 degrees F. Line a baking sheet with parchment paper. Arrange the tomato slices on the baking sheet. Set the garlic and almonds on and around the tomatoes. Drizzle all with the olive oil; bake 75 minutes.
Place the roasted tomato mixture, ensuring you get all the juices from the pan, into a food processor. Add the red peppers, lemon juice and chili flakes, pulse until smooth, and then transfer to a bowl. Cover and refrigerate until needed.
Preheat the oven to 400 degrees F. Place the halibut in a parchment paper-lined baking dish. Drizzle fish with the orange juice; season with salt and pepper. Bake the fish 15 minutes, or until cooked through.
Divide and mound some arugula on each of 4 plates. Set a piece of halibut on the arugula on each plate. Set a dollop of the romesco sauce on each piece of halibut and serve.
Note: Baby arugula is sold in tubs in our produce department. Any leftover romesco sauce can be used the next day as a dip for raw vegetables, or as spread for a sandwich or crostini.
Recipe Options: Instead of halibut, try another fish fillet in this recipe, such as cod or snapper. If you don't care for the spicy taste of arugula, mound at set the fish on a bed of baby spinach. For a sweeter tasting romesco sauce, instead of lemon juice, use orange juice to flavour it.