Step 1 – Mash avocados with a fork in a bowl and season with salt, pepper and lemon juice. Set aside.
Step 2 – Remove seeds and juice from tomatoes. Chop in small cubes. Set aside.
Step 3 – Cut the rolls in half and toast them.
Step 4 – Heat a little oil in a pan over medium high. Cook the steaks on both sides until just done.
Step 5 – Assemble the sandwiches: Spread mayonnaise on both sides of the sandwich bun. Place a layer of beef on the bottom bun. Season with salt and pepper. Add a layer of chopped tomatoes, followed by a layer of mashed avocado. Top off with mayonnaise (optional). Cover with the top bun. Serve immediately.