When making this salad, it's best to prep all your veggies before preparing the fish. Place the romaine and fennel in a large bowl and set the bowl aside. Place all the remaining veggies on a plate and set them aside as well.
Once the veggies and dressing are taken care of, you can start tackling the fish. Start by heating up the oil. Pouring the neutral oil into a large dutch oven. Place it over high heat and pop a candy thermometer in there. We’re aiming for 350°F. ***
Pat two large cod fillets dry with a paper towel. Season with salt and set aside. In a wide, shallow vessel, whisk to combine a 1/4 cup of all-purpose flour and a 1/4 cup of cornstarch. Set aside.
In a separate bowl, whisk to combine 1 cup of all-purpose flour, 1 tsp of baking powder, and lime zest. Slowly stir in the beer until incorporated with some lumps remaining.
Roll the cod fillets in the flour, cornstarch mix before dipping them in the beer batter and dropping them in the hot oil. Fry for about 8 minutes, adjusting the temperature under the oil to keep it hovering around 350°F. Once the fish is golden, transfer the fillets to a cooling rack suspended over a baking sheet. Sprinkle immediately with salt and let cool slightly.
Working quickly, place the romaine and fennel in a large bowl. Add the dressing and toss to coat. Pile the salad into four bowls and top with your desired toppings. Divide fish fillets in half and place one half on top of each salad and garnish with lime. Serve immediately.