Seared Shrimp with Tomato, Lime & Avocado

1 pound tomatoes, cored, seeded, and cut into 1/2-inch pieces 
6 scallions, white and green parts separated and sliced thin 
1/4 cup minced fresh cilantro 
3 garlic cloves, minced 
1 tablespoon fresh lime juice 
1 teaspoon minced canned chipotle chiles in adobo sauce 
1 1/2 pounds extra large shrimp peeled and deveined 
1/8 teaspoon sugar 
4 teaspoons canola oil
1 avocado, pitted, peeled, and cut into 1/2-inch pieces
 
1. Combine the tomatoes, scallion whites, cilantro, garlic, lime juice, chipotle, and 1/4 teaspoon salt in a bowl

2. Pat the shrimp dry with a paper towel and season with 1/4 teaspoon of the oil in a nonstick skillet over high heat, until just smoking. Add half of the shrimp and cook until curled and lightly browned, about 2 minutes.

3. Transfer the shrimp to a bowl and cover with foil. Repeat with the remaining 2 teaspoons oil and shrimp and transfer to the bowl with the other shrimp.

4. Return the skillet to high heat, add the tomato mixture and cook until the tomatoes soften slightly, about 1 minute. Off the heat, return the shrimp to the skilled and toss to coat. Transfer the shrimp to a platter, season with salt and pepper to taste, and sprinkle with the scallion greens and avocado.