>> source: Cook's Illustrated
>> serves: 2
>> total time: 25 minutes

Stir @cream of tartar{3/4%tsp}, @salt{3/4%tsp}, @granulated sugar{1/2%tsp}, and @pepper{1/4%tsp} together in #small bowl{}. Sprinkle mixture on both sides of @field or heirloom tomato{2%4-inch} slices that are 3/4 inch thick. Spread 1 teaspoon @mayonnaise{8%tsp} on 1 side of each slice of bread.

Place 2 slices of @hearty white sandwich bread{4%slices}, mayonnaise side down, in 12-inch skillet. Cook over medium heat, moving bread if necessary for even browning, until underside is golden brown, 2 to 3 minutes. Transfer to cutting board griddled side up. Cook remaining 2 bread slices until underside is golden brown, about 30 seconds. Let cool until griddled side is crisp, about 2 minutes.

Choose ripe tomatoes that are heavy for their size. Larger tomato slices that cover the entire slice of bread are ideal. We developed this recipe with 3/2 by 5-inch slices of Arnold sandwich bread, and the amount of mayonnaise used in step 1 is just enough to thinly cover each slice. Adjust this amount as necessary if your bread has different dimensions.