Pit and peel the avocado half and mash it with a fork. Use a butter knife to spread avocado on one slice of bread. Spread a layer of pesto on the other slice of bread.
Top the avocado bread with a single layer of roasted red bell pepper. Then add a layer of cucumber slices, red onion, olives and spring mix. Use a spoon to sprinkle some balsamic reduction over the lettuce. Place the pesto slice on top, pesto side down.
