Slice tofu block into 6 slices, along the long side of the tofu. Press tofu slices into a paper towel to soak up some water. Chop each slice into 8 cubes. In a small bowl, mix tamari, brown sugar, cornstarch, and water. Set aside.

Heat a large sauté pan over medium-high heat. When the pan is hot, add 1 tablespoon of sesame oil.

Add tofu cubes and cook for 8-10 minutes, until the cubes are well browned. Flip tofu cubes periodically so that you get browning on more than one side. Tongs work very well for this. Pour in tamari sauce and watch it sizzle. If the sauce turns thick immediately, add a splash of water. Stir for a minute and dish up the tofu to a plate.

Bring 5 cups of water (just over a liter) of water to boil. Salt the water. When water has boiled, turn off the heat and throw in rice noodles. Let them sit in there for 5 minutes. The noodles should be al dente. Drain water and rinse noodles under cold water. Set aside.

Mix coconut milk, curry paste, and tamari together and set aside.

Wipe down sauté pan. Heat pan over medium heat and add another tablespoon of sesame oil. Add onions and cook for 2 to 3 minutes, or until it softens. Add lemongrass, if using, and stir for about 30 seconds. Stir in red cabbage and cook for a minute. Toss in shredded carrots and a pinch of salt and cook for another minute. Add cooked rice noodles and coconut milk mixture. Stir everything for a minute, and mix in tofu cubes. Turn off heat and serve. Garnish with cilantro, sesame seeds, and red pepper flakes if you like.