While the lentils are simmering, heat 3 tbsp of olive in in a 12 inch heavy skillet or pot over medium high heat. Saute the onions with 1/2 tsp salt and 1/2 tsp pepper stirring them through. Reduce the heat to medium low and cook, stirring occasionally until the onions are golden brown and softened. Keep and eye on them and stir more regularly as they get close to being done. This should take around 40 minutes. Then increase the heat to medium and keep cooking till golden brown, about another 5 or so minutes.
This is a great recipe to prep for: Remove the ribs from the kale, chop and store in a plastic bag overnight.
Cook lentil and onion mixture in advance and store in a container.
Then all you'll need to do is grate the cheese, reheat the onions and lentils over low in a large skillet, cook the pasta, add the kale and then toss it all together as per above.