Any pluot (a cross between a plum and an apricot) or plum will work well in this salad. Make sure that your fruit is nice and ripe – let it sit out for a day or two if you need to. The flesh should be tender but not squishy. The cherry tomatoes should also be fragrant and ripe. Store-bought cherry tomatoes will work, but if you can find a friend with a garden, all the better.
I like the addition of marjoram here, it has an anise-like quality to it that backs up the fennel nicely. However if that’s not a favorite flavor of yours, use less or leave it out all-together.