- 3/4 teaspoon fennel seeds
- 1/8 teaspoon crushed red pepper flakes
- 1 tablespoon olive oil
- 1 small fennel bulb, thinly sliced, plus fennel fronds for garnish
- Kosher salt, freshly ground pepper
- 1 1/2 cups store-bought marinara sauce, preferably with no sugar added
- 4 4-ounce pieces skinless flounder fillet
- Coarsely chopped fresh tarragon
- Special equipment: A spice mill (optional)
- Coarsely grind fennel seeds and red pepper flakes in a spice mill or with a mortar and pestle. Alternatively, place in a resealable freezer bag. Crush with a rolling pin or large skillet. Set aside.
- Heat oil in a large skillet over medium-low heat. Add sliced fennel, season with salt and pepper, and cook, stirring often, until soft, 10-12 minutes. Add spices and cook, stirring often, until spices are beginning to darken, about 1 minute.
- Add marinara sauce and 1/2 cup water to skillet; bring to a simmer and cook to meld flavors, about 5 minutes. Season with salt and pepper.
- Season fish with salt and pepper and fold fillets in thirds or in half to form packets. Place fillets in sauce. Cover skillet and reduce heat to medium-low. Cook until fish is opaque and beginning to flake, 12-15 minutes.
- Divide fennel-tomato sauce and fish among shallow bowls. Sprinkle tarragon and fennel fronds over.