Baste the chicken breast with olive oil and place on a medium hot grill. While the chicken is grilling, split the bun, brush it with olive oil and drop on the grill to mark it, also baste and grill the onions until they are starting to turn translucent.
A simple guacamole is easy to make: take one avocado and mash it together with lime juice, salsa and salt to taste. Add chopped cilantro and green onions and you’re done. Assemble the sandwich ingredients in quantities to your taste and enjoy!