Heat the oven to 400°F. Place the poblano on a foil-lined baking sheet and roast for 15 to 20 minutes, turning it once, until the skin is blistered. Transfer it to a bowl and cover for 10 minutes, then peel away the skin, remove the stem and seeds, and cut the pepper into strips.
While the poblano rests, make the corn salsa. Combine the corn, red bell pepper, cilantro, lime juice, olive oil, and a pinch of the measured salt in a bowl. Stir and set aside.
In a large bowl, combine the ground turkey, egg, breadcrumbs, onion, garlic powder, the remaining salt, and black pepper. Mix gently until just combined.
Pat about half of the turkey mixture into a loaf shape on a parchment-lined baking sheet. Arrange the roasted poblano strips over the center, then place the pepper jack stick on top. Keep the filling away from the edges so it stays enclosed.
Cover the filling with the remaining turkey mixture. Pinch the edges together and smooth the surface to seal the cheese and poblano inside.
Bake for 40 to 50 minutes, until the center reaches 165°F on an instant-read thermometer. Rest the meatloaf for 10 minutes before slicing. Serve with the corn salsa spooned over each slice or alongside.