In a medium pot, combine lentils and water. Bring to a boil, then reduce heat and simmer uncovered for 20-25 minutes until tender but not mushy. Drain and let cool.
In a large bowl, combine cooled lentils with chopped red onion, cherry tomatoes, and fresh dill.
In a small bowl, whisk together lemon juice, olive oil, salt, and pepper to make the dressing.
Pour the dressing over the lentil mixture and toss gently to combine.
Serve chilled or at room temperature.
Notes
This lentil salad can be prepared a day ahead and stored in the refrigerator for up to 2 days. Garnish with extra dill before serving if desired.