Place a medium saucepan onto a medium/high heat and bring to the boil, add the vinegar.
Cut the tomatoes in half and add the butter to a medium frying pan, place the tomatoes into the frying pan cut side down, fry for 2-3 minutes until you have a nice colour, then turn over and cook for a further 2-3 minutes.
Crack 1 egg into a small ramekin, lower the heat of the water to just simmering, Slowly pour the egg into the water, crack the second egg into the ramekin and pour that into the water on the other side of the saucepan, allow them to cook for 3-4 minutes for soft yolk eggs, cook longer if you prefer a hard yolk.
Slice the avocado and run a knife through the avocado flesh, then scoop out ready to place on the cooked tomatoes.
Remove the eggs to some kitchen paper to drain off the excess water, when the tomatoes are cooked, place them onto a plate, add the avocado and top with the poached eggs.