Bring water and lentils to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until lentils are almost tender, about 15 minutes; add bulgur and salt. Cover saucepan and remove from heat; set aside until bulgur is tender and water is absorbed, about 20 minutes.
Heat 1 teaspoon olive oil in a skillet over medium heat; cook and stir onion and garlic until until tender and fragrant, 5 to 10 minutes. Add tomatoes and red bell pepper; cook and stir until red bell pepper is tender, 5 to 10 minutes.
Combine bulgur-lentil mixture and vegetable mixture in a bowl; add balsamic vinegar and 2 tablespoons olive oil and toss to coat.
You can change the oils and vinegar. I've used lemon-infused olive oils and fig-infused balsamic vinegar, for example. Adding avocado is always a good choice. It really doesn't look pretty, but it tastes great!
If the bulgur seems dry after sitting for 20 minutes, add more water.