Heat 1/2 teaspoon oil in a large wide skillet over medium-high heat for 1–2 minutes until shimmering.
Add the diced onion and sauté 3–4 minutes until it begins to brown.
Add the ground beef and cook 4–5 minutes, breaking it up with a spatula, until no pink remains; drain excess grease.
Return the pan to low heat and add 2 tablespoons taco seasoning, 1/2 teaspoon garlic powder, 1/2 teaspoon paprika, 1/2 teaspoon salt, 1 tablespoon tomato paste, 1/2 cup salsa, and 1 cup frozen corn.
Turn heat to medium-high, stir and cook 1–2 minutes until the liquid is mostly absorbed and the corn is warmed, then remove from heat and set aside.
Place one 8-inch tortilla on a cutting board and sprinkle about 2 tablespoons cheese over half the tortilla. Spoon about 1/4 cup of the beef mixture over the cheese, then top with another ~2 tablespoons cheese. Fold tortilla in half to form a half-moon. Repeat to assemble remaining quesadillas.
Heat a clean skillet over medium-high and lightly oil or spray the pan. Cook each quesadilla 1–2 minutes per side until golden brown and the cheese is melted, adjusting time as needed; the first may take slightly longer.
Transfer cooked quesadillas to a board, slice each in half into triangles, and serve.
