Preheat the oven to 400ºF and line a baking sheet with parchment paper. Heat a small skillet over medium heat and add the oil. Once hot, add the onion and cook for four to five minutes or until softened. Remove from heat and set aside.
In a small bowl, add the ground flax seeds and water and let sit for a few minutes until thickened slightly.
In a food processor, add the lentils, onion, flax seed mixture, nutritional yeast and almond flour. Pulse until combined and the dough starts to hold together.
Using slightly damp hands, roll the dough into golf-ball sized balls. Place on the baking sheet. Bake for 25 minutes, flipping halfway through.
While the lentil meatballs are in the oven, cook the pasta according to package directions. Drain and add the pasta back to the pot. Add the tomato sauce and mix. Divide evenly between plates and top with the lentil meatballs. Enjoy!