Meanwhile, in a medium bowl, combine red onion and vinegar. Sprinkle with the sea salt and let sit until onion softens, about 5 minutes.
In a separate kettle, boil water, enough to fill a large skillet.
Place lentils in a large skillet. Add enough of the boiling water to come to about 1″ above the lentils.
Bring the water to a simmer and cook until tender but not mushy, about 20-30 minutes.
Drain well in a colander or mesh sieve. Shake off all visible moisture. Transfer to a separate bowl.
While the lentils are still warm, add red onion, olive oil, the garlic and freshly ground black pepper to taste.
Stir gently, avoiding mashing any lentils. Let sit to cool to room temperature.
Once lentil mixture is cool, add the herbs and combine. Adjust seasonings if necessary.