Season the fish lightly with salt on all sides and let it rest while you prepare the poaching liquid.
Combine wine, vinegar, water, thyme, zest, juniper berries, and bay leaves in a large pot. Season with salt. Heat over medium-high heat until 180°F.
Add the fish to the poaching liquid. Reduce heat to low. Use a thermometer to maintain the heat between 165°F and 175°F. Cook for 8–10 minutes per inch of thickness. Remove from heat and cool the pot to room temperature, and then store in the liquid in the refrigerator for 2 hours and up to overnight.
To serve, make a salad by tossing apple, fennel, radishes, and cilantro with lemon juice and olive oil.
Remove the fish from the cooking liquid. If the skin has been left on, gently remove it by using a fish spatula. Discard the skin.
Spread Green Goddess Dressing on a plate. Arrange the salad on the plate. Place the fish atop the sauce and salad.
Can be made up to a day ahead.