Make an incision down one side of the skin of the roe, open it up and use a teaspoon to scrape out the eggs, then drop them into a food processor. Grate the stale bread (which should be nice and dry) into fine crumbs and add these to the roe. Coarsely grate the onion through the setting on your grater that you would do a kiddie’s Cheddar for Bolognese, then scrape into a small sieve positioned over the processor bowl and use a spoon to press the juice through the sieve over the roe and the bread. Discard the pulp. Add the garlic to the mix.
Secure the lid of the processor and hit go. Now slowly dribble in the oil. The mixture will become quite thick. At this point, add the water and lemon juice according to your judgement, stopping the motor every now and again to taste the taramasalata so as to get the right consistency and acidity; you can put lemon in, but you can’t take it out. The mixture should not be too loose, but only just hold its own and be very smooth and creamy.
Scrape the contents into a bowl. Eat, remembering in your eagerness not to ambush your delicate fingertips on the hot steam within the pitta bread. I like to have butter on the pitta as well as tarama.