Combine water and buckwheat in a saucepan; bring to a boil.
Reduce heat to medium-low, cover the saucepan, and simmer until the buckwheat is firm yet tender to the bite.
Rinse buckwheat under cold water and drain.
On a big bowl, add cherry tomatoes, red onion, olive oil, parsley, fennel seed, cayenne pepper, lime juice and grounded pepper together in a large bowl until evenly combined. Add buckwheat and stir gently; top with goat cheese.