1With a wooden or metal skewer, stab each tomato ten times; place in a glass bowl.
2Puree the tomatoes, onions and salt in the bowl of a food processor. Pour it into a fine sieve set over a bowl and push on the solids, getting out as much of the liquid as possible. Discard the solids (or save them for soup!). Add the zest and juice of the lemons, along with everything else (except the margarita salt) to the tomato juice. Pour the mixture over the cherry tomatoes and refrigerate for up to a week, but at least 3 days.
3To serve, spear each tomato with a toothpick or wooden skewer and set in a shallow bowl with some of the liquid (spears up so they don't get wet!).