Strain the olives, then measure the liquid and top up with warm water to make 250ml.
Put the strained olives and the liquid into a bowl, then stir in the yeast, sugar and 50g of sesame seeds.
Add the flour, mix to a soft, sticky dough, cover and leave for 10 minutes.
Lightly oil a patch of worktop just large enough to knead on, then give the dough a short, 10-second knead.
Return the dough to the bowl, cover and leave for 10 minutes more.
Repeat this quick knead twice more at 10-minute intervals, then leave the dough, covered, for 90 minutes.
Meanwhile, line the base of a tray with nonstick baking paper, grind the herbs as fine as you can, then tip on to a large dinner plate and mix with a tablespoon of sesame seeds, the sumac (if using) and lemon zest.
On another plate, have ready a wet square of kitchen towel.
Pat the dough into a rectangle on a clean worktop dusted with a little flour, then roll it up tightly into a snug scroll, making sure all the olives are tucked in.
Next, tightly roll the ends of the loaf, so they pinch in and the loaf has a shape a bit like a lemon.
Roll the loaf on the wet towel, then roll it in the herb and spice mix.
Place on the tray seam-side down, cover and leave to rise for 90 minutes.
Slash the top and bake at 220C (200C fan-assisted)/425F/gas mark 7 for about 40 minutes.
