Preheat oven to 180 degrees C. Grease a shallow baking dish.
Rub the fish fillets with 1 tablespoon of lemon juice then season with salt and pepper. Place the fillets into the prepared baking dish then press the coriander leaves onto the top of the fish. Bake in the preheated oven until the fish flakes easily with a fork, 15 to 20 minutes.
Meanwhile, melt the butter in a frypan over medium heat. Stir in the spring onions, capsicum, garlic and chilli flakes until the vegetables have softened, about 5 minutes. Pour in the white wine and season with dill and tarragon.
Simmer for 2 minutes then add the chicken stock, cream, Parmesan cheese and remaining 1 tablespoon of lemon juice; season with salt and pepper to taste.
Bring to a boil over medium-high heat, then dissolve the flour into the water and stir into the boiling sauce. Return to a boil then reduce the heat to medium-low and simmer until the sauce has thickened, about 10 minutes. Spoon the sauce over the fish and top with slivered almonds.