You say to-may-to
And I say to-mah-to…
The only time of year to make tomato sauce from fresh produce is right
around the corner, and while the weather has not exactly been
cooperative down here, we do have some great tomatoes coming.
If you're looking for slicing tomatoes, head for a stand that sells heirloom tomatoes. Sure, they're knobbly, strange colors and slices of them look like they were beaten with an ugly stick, but the taste will be what tomatoes should be (and what they were when our grandparents were alive). Brandywines are pinkish-red and tend to be larger; Cherokee Purple are, as you suspect, deep purple, with less acidity than Brandywines. Green Zebras look like tiny eggplants and are green when ripe, which can give diners pause to funny effect.
If you're looking to make sauce, go for Italian tomatoes such as San Marzano-types (egg-shaped, with a little nipple on the bottom end). Fiaschetto are egg-shaped, with a nipple on the bottom end, and Maremmamo are nearly perfectly spherical. Farmers' market sauce should be simple, just a little onion or garlic, lots of very good olive oil, tomatoes, salt, pepper, basil… and a little bit of wine or vodka, because tomatoes have alcohol-soluble flavors.
For salads, choose pear tomatoes; these are cherry tomatoes with a little nubbin on top. Yellow pear tomatoes are often sweeter and less acidic than their red cousins; they go perfectly in a salad with romaine, cooked bacon pieces, torn crusty bread and basil.
When picking tomatoes, you want to avoid bruises. You may see seams of tough-looking green or brown material; these are normal on ridged tomatoes and the seams don't go very far into the tomatoes; you can peel them away. You don't want sponginess, or rot spots, or mold on the stem. Tomatoes sold on the vine should come off with almost no effort; if you have to twist more than a couple of times, the tomatoes probably aren't ripe yet.
Don't ever store tomatoes in the refrigerator; they'll go hard and wooden-tasting even left overnight. Keep them out on the counter and use them quickly.