Place the spaghetti in a small pan along with the prepared cherry tomatoes, garlic, anchovies, olives, basil leaves and olive oil. Season generously with black pepper and add the liquid smoke if using.
Add 250ml of the boiling water and place over a medium-high heat. Cook for 15–20 minutes, stirring occasionally, until the spaghetti is just cooked through and the sauce has thickened.
Towards the end of cooking the sauce may become too thick and dry for the pasta to finish cooking, causing it to stick on the bottom of the pan. If so, add some of the remaining water, a little at a time, to help loosen the sauce.
Once cooked through, stir in the capers and serve immediately, garnished with the reserved sprigs of fresh basil.