Set a medium saucepan on the stove and pour in the water. Add 1/2 teaspoon of the salt, cover the pan, and bring the water to a boil over high heat.

Set a large skillet on a second burner over medium heat. Add the olive oil and 1 tablespoon of the butter.

Put the sliced onion into the skillet. Cook for 4 minutes, stirring a few times, until the onion starts to soften.

Add the sliced cabbage to the skillet with another 1/2 teaspoon of the salt. Stir well so the cabbage gets coated in the oil and butter.

Cook the cabbage for 5 minutes, stirring every minute or two, until it starts to wilt and shrink.

Add the caraway seeds and the black pepper to the skillet. Cook for 8 to 10 minutes, stirring often, until the cabbage is very soft and browned in spots.

When the water in the saucepan is boiling, add the buckwheat groats to the saucepan. Stir once, lower the heat to low, cover the pan, and cook for 10 to 12 minutes, until the water is absorbed and the groats are tender.

Add the drained white beans to the cabbage in the skillet. Pour in 1/4 cup of water, stir gently, and cook for 3 minutes until the beans are heated through.

Taste the cabbage and beans in the skillet. Add more salt and a little more black pepper if the mixture tastes flat, then keep the skillet on low heat while you finish the sauce.

Put the sour cream in a small bowl. Add the lemon zest, 1 tablespoon of lemon juice, half of the chopped dill, and a small pinch of salt.

Stir the sour cream mixture until smooth. Taste it and add another small squeeze of lemon juice if you want a sharper sauce.

When the buckwheat is done, turn off the heat under the saucepan. Add the remaining 1 tablespoon of butter to the saucepan and fluff the kasha with a fork until the butter melts through the grains.