Before you do anything, cut your tomato into thick slices and place them on a paper towel. Sprinkle with a little bit of flaky salt and let them sit for a few minutes (5 should be enough). Blot away the excess moisture with a paper towel. Salting helps draw out excess moisture, which helps prevent a soggy sandwich and concentrates the tomato's flavor.
Meanwhile, toast the bread to your liking. I like doing that on a skillet with a little bit of olive oil or butter. Either way, let it cool for a little bit while you chop your chives or something.
Slather one slice of bread with kewpie. I like a light layer, but use your own judgment.
Layer as many tomato slices you can on top of one slice of toast. Sprinkle generously with flaky salt and drizzle with chili crisp.
Garnish with black pepper and chopped chives. Top with the other piece of toast, cut vertically, diagonally, or not all. Eat immediately, with a side of napkins preferably, and enjoy those summer juices running down your chin.