In a small bowl, whisk together oil, lime juice, garlic, and cayenne. Season with salt.
Scoop out meat from avocado halves and chop. Transfer to a bowl and add bell pepper, tomatoes, scallion, and cilantro.
Drizzle with dressing and season with salt. Gently stir to combine. Spoon mixture into avocado shells. Garnish with cilantro leaves.