Tips for the ultimate tomato sandwich:

Slice your tomatoes in ¼-to-½-inch wheels. Lay them on a cutting board, cut side up, and season generously (more generously then you think you need) with salt and freshly ground black pepper. Let sit for at least 5 minutes, so that some of their juices release.

Apply a thick layer of mayonnaise to one side of two slices of bread; the mayonnaise will help keep the tomatoes’ juice from soaking through the bread. Layer the seasoned tomatoes onto the mayonnaise side of one slice of bread; sandwich with the other slice of bread and enjoy. 

Homemade Mayonnaise:

1 egg yolk

½ cup olive oil

½ cup grapeseed oil

1 teaspoon Dijon mustard

1 teaspoon lemon juice

Kosher salt

  Making mayonnaise is about creating an emulsion where oil is suspended in liquid so that the two don’t separate—it’s the same concept behind vinaigrette, only now with the presence of an egg yolk, a binding agent that gives it a thick and creamy texture. There are a few tricks to creating an emulsion: drizzle your oil very slowly and whisk very quickly. If your mayonnaise “breaks”—that is, if the oil and egg yolk start to separate, you can fix it by whisking the broken emulsion into a bowl with new egg yolk.

Buying:

The scent: Tomato plants have an entirely unique smell, which lingers at the base of the fruit for a few days after it’s picked. Take a whiff of the tomato’s core (that rough spot where the fruit connected to the plant); you should be able to smell the faint woody-yet-sweet scent of the tomato plant if the tomato is fresh. 

The weight and color: The best way to know if a tomato is ripe is to hold it in your hand gently (don’t squeeze it! How soft it is won’t tell you if it’s ripe) and feel the weight. It should be heavy for it’s size. Compare the weight to a few other tomatoes and choose the heaviest. When it comes to tomatoes – heirloom or not – you want the ripe color, whether it is red, orange, yellow or green – to go all the way up to the top of the shoulders. A bit of green at the very top, near the stem, is natural, but you want the color at the very bottom of the tomato to go up the sides of the tomato and cover 80 to 90 percent of the skin.

The skin: Heirloom tomatoes aren’t as uniform as their year-round grocery store cousins, so it’s completely normal for their skin to have splits or small blemishes. However, you want to avoid tomatoes with wrinkled skin, which is a sign of age.

Timing: It’s best to shop for tomatoes a day or two before you plan to use them, so that they can finish ripening naturally to total perfection. Most farmers bring tomatoes with a range of ripeness to market, so ask them to help you pick out a tomato based on when you’ll be eating it. If you’re making sauce or soup, ask the farmer for tomatoes that are maybe one or two days past their prime: they’ll likely be on sale and it won’t make a difference when you’ve whirred them into liquid.

  Storage:

Tomatoes should be kept at room temperature, uncovered. Never put whole tomatoes in the fridge. If you have a large tomato and won’t eat all of it, you can wrap the uneaten part in plastic wrap and store it in the fridge. The texture will suffer in the fridge, so keep that in mind when using the second half of the tomato. 

Heirloom tomatoes are prone to cracking. If the crack has scarred over, simple cut that part away before eating. Any tomatoes that are cracked and show the inner flesh should be eaten that day.