Brush each slice of bread with olive oil, then toast until golden brown, about 3–4 minutes per side.

Halve and pit the avocado, scoop into a bowl, mash until smooth but still slightly chunky, then mix in lemon juice, salt, and pepper.

Drain canned tuna, flake into a bowl, then stir in mayonnaise, herbs, and red onion until well combined.

Spread avocado mix over each toasted slice, top with tuna mixture, and garnish with cherry tomatoes or microgreens.