Place the corn in a steamer basket set over a saucepan of simmering water. Cover and steam 8 minutes.
Meanwhile, grate the lime zest into a small bowl and squeeze in 1 tablespoon lime juice. Add the sour cream, cilantro, hot sauce and 1/4 teaspoon salt and mix well; set the dip aside.
Remove the corn from the steamer basket and let cool slightly, then cut the kernels off the cobs. Combine with 1/2 teaspoon salt in a bowl.
Line a large baking sheet with paper towels, then arrange the wonton wrappers on top in a single layer. Place 1 teaspoon corn, 1/2 teaspoon tomato, 1/2 teaspoon avocado and 1/4 teaspoon red onion in the center of each wrapper.
Heat about 1 1/2 inches of vegetable oil in a large pot until a deep-fry thermometer registers 375 degrees (or place a wooden skewer in the oil to test the temperature; bubbles should form around it).
Moisten the edges of each wonton wrapper with water, then fold in half diagonally to enclose the filling and form a triangle; press gently to seal. Working in batches, lower the wontons into the hot oil with tongs and fry about 1 minute. Flip and fry another 30 seconds, or until light golden. Transfer to paper towels to drain. Serve with the cilantro-lime dip.
Photograph by Ngoc Minh Ngo
Recipe courtesy Elizabeth Spano for Food Network Magazine