In a medium bowl or 1-quart liquid measuring cup, combine the tomato puree, boiling water, tomato paste, sugar, 1 teaspoon salt and ½ teaspoon black pepper. Whisk until the tomato paste dissolves.

In a heavy-bottomed 12-inch nonstick skillet, combine the oil, garlic and pepper flakes. Set over medium-high and cook, stirring, until the garlic no longer smells raw, 1 to 2 minutes. Stir in ¾ cup of the tomato mixture. Place the spaghetti in the center of the pan with the noodles parallel to each other, distributing them in an even layer (See NOTE below). Using a spatula, press down on the noodles. Cook without stirring and occasionally pressing down until the tomato mixture at the edges is reduced and deeply browned and the pasta is sizzling, about 5 minutes.

Slide a spatula under half of the spaghetti and flip the noodles, then do the same with the second half; the bottom of the noodles should be spottily charred. Once again, distribute the pasta as best you can in an even layer. Ladle on 1 cup of the tomato mixture, pouring it over and around the pasta. Cook without stirring but pressing down, until the liquid is reduced and once again browned at the edges of the pan and the pasta is sizzling, 3 to 4 minutes.

Flip the pasta in the same way and ladle on another 1 cup tomato mixture. Cook in this way until the pasta is al dente but crusty and spottily charred; this will require another 2 or 3 additions of tomato broth; you may not use all the broth. Finish with a flip of the pasta (not with an addition of broth). Off heat, taste and season with salt and black pepper.

NOTE: Don’t try to squeeze 1 pound of pasta into the skillet. It’s too much for the amount of sauce and will crowd the pan. Also, don’t stir the pasta as it simmers. Undisturbed cooking with only two flips allows the spaghetti to develop crispness and deep, flavorful charring. Legit recipe from Bari, Italy.