Line an 11x9-inch (28x23cm) baking sheet or tray with parchment paper making sure it stretches up the sides of the pan.
Lightly grease the paper by using a pastry brush to coat it with olive oil. This will ensure the honey and sesame mix doesn't stick to it.
Heat a large frying pan or skillet over a medium heat. Add the sesame seeds and toast over until they're golden brown, about 4-5 minutes. Remove from the heat and tip them onto a plate. Set aside for now.
Pour the honey into the same skillet and reduce the heat to medium-low. Let the honey come to a boil so it looks foamy in the pan, about 3-4 minutes (see note 1).
Once it's boiled, pour the toasted sesame seeds into the hot honey and stir well to ensure it's all combined. If using the lemon zest and salt, stir these in now too. The mixture should have quite a thick consistency.
Pour the honey sesame mix onto the prepared pan and spread into a thin layer with a wet wooden spoon.
Place another oiled sheet of parchment paper over the top and roll over it with the base of a glass. This helps to flatten out the top and make it even.
Set aside to cool for 20-30 minutes at room temperature then slice with a sharp knife into any shape you like. Small squares, rectangles or diamonds all look good.
You can enjoy the sesame candy as-is or place in the fridge for 5-10 minutes so it's slightly more firm.
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Notes
Note 1: Don't burn the honey! It's very important that the honey foams so it will set once cooled. However, keep an eye on it and ensure it's not sitting over a high heat. Burnt honey will make these sesame bars taste very bitter.Note 2:Store any leftovers in an airtight container between layers of parchment paper so the bars don't stick together.