Finely slice the red onions and leave to soak in a bowl with the vinegar until they are soft & pink (a few minutes).
Bring a pan of water to the boil, enough to cover the eggs. When it’s on a rolling boil, add the eggs & cook for 4 minutes 20 second for soft eggs or 5 minutes for a slightly stickier yolk. When finished cooking, run under cold water & peel gently.
Toast the bread and portion the sliced avocado evenly over each piece.
Top with the soft eggs, pickled onion, sliced tomatoes, and grated cheddar.
Season and serve with a wedge of lemon and a pinch of fresh garden herbs.