Wash and dry all produce. Preheat broiler to high. Halve poblano lengthwise and remove stem, seeds, and core. Cut scallions in two near the point where the white part turns green. Thinly slice greens; leave the whites whole. Rub corn, poblano, and scallion whites with a large drizzle of olive oil.

Season corn, poblano, and scallion whites with salt and pepper, then toss with Southwest spice. Place on a baking sheet and broil until lightly charred, about 3 minutes for scallions and 8-10 minutes for corn and poblano, turning halfway through. Remove from broiler and let cool.

While veggies broil, zest 1 tsp zest from lime, then halve and squeeze 2 TBSP juice into a medium bowl. Dice tomato. Mince chili, removing ribs and seeds for less heat. Place tomato and chili (to taste) in bowl with lime juice. Add a large drizzle of olive oil. Season with salt and pepper. Toss to combine.

Mix sour cream in a small bowl with 1-2 TBSP water, or just enough to thin to a drizzling consistency. Season with salt and set aside. Once veggies are cool enough to handle, cut corn kernels from cob. Remove fuzzy root ends from scallion whites, then chop. Cut poblano into small pieces. Stir corn kernels, scallion whites, poblano, and lime zest in a large bowl. Season with salt and pepper, then stir in half the cheese.

Rub one side of each tortilla with a drizzle of olive oil and place oiled-side down on another baking sheet. Arrange veggie mixture on one half of each tortilla, then fold tortillas over to create quesadillas. Place under broiler and broil until tortillas are lightly browned, 1-2 minutes.

Flip quesadillas and sprinkle remaining cheese on top. Return to broiler and broil until cheese bubbles, 1-2 minutes more. (TIP: Keep an eye out for any burning.) Cut each quesadilla into thirds. Spread tops with crema and spoon salsa over. Sprinkle with scallion greens and serve.