Bring a medium pot of shallow water to a simmer. Add the block of tempeh and simmer for 10 minutes. Drain the tempeh and pat it dry. Allow the block to cool and crumble it into pieces (whatever size you like—they can be big crumbles or smaller crumbles).
Heat the oil in a large skillet over medium heat. Add the tempeh, thyme, oregano, paprika, and black pepper. Cook the tempeh for about 5 minutes, stirring often, or until it's lightly browned, adding a little extra oil as needed. Add the tamari or soy sauce to the tempeh crumbles and cook for another minute. Season the crumbles to taste with additional herbs or tamari before removing the crumbles from the skillet.
Heat the olive oil in the same skillet over medium heat. Add the chopped onion. Saute the onion for 5 minutes, or until clear and soft. Add the garlic and cook, stirring constantly, for 2 minutes, or until the garlic is fragrant but not burning. Add the diced tomatoes, tomato paste, and sugar. Allow the sauce to come to a simmer, then reduce the heat to low. Stir in the tempeh, taste, adjust seasonings as needed, and set the skillet aside.
To make the polenta, bring the 4 cups water and salt to boil in a medium-sized saucepan over medium heat. Whisk in the polenta and reduce heat to low. Simmer the polenta, stirring constantly, for 15 to 35 minutes (this can vary wildly, depending on the type of polenta you use), or until the polenta is thick and pulling away from the sides of the pot. Stir in the soy or almond milk, oil or buttery spread, and nutritional yeast. Season to taste with extra salt and black pepper as needed.
To serve, top a heap of polenta with the tomato and tempeh mixture, as well as some chopped fresh herbs or torn basil, if you like.
Gena Hamshaw is a certified nutritionist, recipe developer, and food blogger. She shares her latest culinary adventures at The Full Helping. She's the author of two cookbooks, Food52 Vegan (2015) and Choosing Raw (2014). She enjoys yoga, sweet potatoes, cashews, and things that are smothered in sauce.