Preheat the oven to 200°. Set a rack on a baking sheet next to the stovetop. In a medium bowl, whisk together the lemon curd, vinegar and 1/2 teaspoon salt.
Fill a large saucepan with enough oil to reach a depth of 2 inches and heat over medium-high heat until it registers 350° on a deep-fry thermometer. In a medium bowl, whisk together 1 cup water, 3/4 cup flour, the cornstarch, baking powder and 1/2 teaspoon salt.
In another medium bowl, toss the chicken with the remaining 2 tablespoons flour and a pinch of salt. Working in 3 batches, coat the chicken with the batter and, using tongs, add each piece to the hot oil. Fry until golden, about 5 minutes. Using a slotted spoon, transfer the fried chicken to the prepared rack and keep warm in the oven. Let the oil return to 350° between batches and repeat with the remaining chicken.
Add the bell pepper and scallions to the hot oil and fry until crisp-tender, about 2 minutes. Using a slotted spoon, transfer the vegetables to the lemon curd sauce. Arrange the chicken on a platter and spoon the sauce on top.