Adjust the oven rack to the middle position and heat the oven to 350°F. Line a rimmed baking sheet with aluminum foil to make cleanup easier.

Toss the panko with the oil in a 12-inch nonstick skillet over medium-high heat. Cook, stirring often, until the crumbs are well browned and smell nutty, about 5 to 10 minutes.

Slice each jalapeño in half lengthwise through the stem. Use a small spoon to scrape out the ribs and seeds, leaving the walls of the pepper clean.

Stir together the cheddar, cream cheese, scallions, lime juice, chili powder, and salt in a bowl until the mixture is uniform and creamy.

Spoon the cheese mixture evenly into the prepared jalapeño halves and place them on the baking sheet. Press the toasted panko onto the cheese and spray the tops lightly with vegetable oil spray.

Bake until the peppers are slightly softened and the cheese is bubbling, about 15 to 20 minutes.

Serve warm, while the cheese is still melty and the topping is crisp.