Heat a large skillet over medium-high heat and add the poblano pepper, skin side down, along with the ears of corn, and cook, turning the corn occasionally, until the kernels are golden brown and the pepper skin is dark and blistered, about 10 minutes. Remove the pepper and corn and let cool. Peel and discard the blackened skin from the roasted pepper, then coarsely chop. Cut the kernels off the cobs and set aside.
In a medium bowl, toss together the roasted pepper, corn kernels, onion, roasted tomatoes, garlic, cayenne and cilantro. Add the lime juice and season to taste with salt. The salsa can be kept in the refrigerator for up to 4 days.