Soften the onion, in a medium-large pot, in about a 1/4 cup water, till the water is just about gone.
Meanwhile, heat oil over medium in a small pan. Add garlic and saute for just a minute or so, not quite till golden. Add remaining spices and stir to coat. Saute these for another couple of minutes, reducing heat if necessary. (You can use more oil if you wish. The spices will be sort of crumbly rather than pasty, but the flavor still develops just as well.).
Add spices to onion, and stir to coat well-a silicon spatula works really well for this! Or a wooden or regular spoon probably would too.
Add the 6 cups water, and cover to bring to a boil faster. When a boil has been achieved, add the split peas and let it continue to bubble for a minute.
Reduce heat to very low, cover and let simmer for about 1 1/2 hours, stirring occasionally, till the split peas are soft and mostly lost their shape.
Add lime juice, salt to taste, and serve. Slices of whole-wheat bread are wonderful for dipping. Or, if you use a little less water (say 1/2-1 cup less) this would be thick enough to serve like a dahl,over rice. Enjoy!