Place lentils and 1 TBSP baking soda in a glass bowl and full bowl with enough cool water to cover the beans. Cover and allow beans to soak overnight.
In the morning, rinse and drain the beans.
In a large sock pot, add butter and onion. Saute until translucent. Add caraway seeds and coriander and saute.
Add lentils to pot, add just enough water to cover lentils. Cook low and slow. Stir occasionally adding a little more water, enough to cover, when stirring. Cook on low for about 4 hours.