Combine pear, red onion, carrot, bell peppers, jalapeno pepper, green onion, cilantro, lime juice, garlic, and cayenne powder in a bowl. Season with salt and pepper. Set pear salsa aside to allow flavors to meld.
Heat olive oil in a skillet or grill pan over medium-high heat. Season tuna with chili powder, cumin, salt, and pepper; add to the skillet. Sear for 3 minutes. Splash 1 tablespoon lemon juice over the tuna. Turn tuna over and splash remaining lemon juice on the second side. Continue cooking until center is medium-rare, about 3 minutes more.
Transfer tuna to a plate and let rest for 5 to 10 minutes. Slice and serve over tortillas. Top with pear salsa.
