Line a baking tray with a silicone mat and set aside. Prepare a water bath by filling a roasting tin halfway with water. Set aside.
Combine the sugar and water in a small saucepan and set over medium heat. Leave the sugar to dissolve and then turn up the heat to medium-high. Allow the sugar syrup to simmer and bubble until you have a light golden caramel, it will take 7-10 minutes. Do not put any utensils in the pot to stir it (this will help with your clean up later). Some like to use sugar thermometers, but I don’t think it is necessary for this recipe. Just use your eyes – you will see when you have a light golden color.
Once your caramel is done, remove the pot from the heat and gently dip the bottom of the pot into the prepared water bath. This will stop the caramel from continuing to cook and color. Place the pot on a trivet.
Spear a toothpick into a tomato and dip halfway into the caramel then directly into the sesame seeds to coat. Place on the prepared baking tray. Repeat with the rest of the tomatoes, working quickly so you finish before the caramel hardens. Leave at room temperature.
I don’t usually include notes for how to clean up, but when making caramel, I thought it might be useful. Once finished with the caramel, fill the pot with water. Place over medium-high heat and bring to a gentle simmer. The caramel will soften and the sugar will dissolve again into the water. Once you have only liquid in the pot, simply pour out into the sink and wash your pot. No more sticky caramel!