If you use dry (not packed in oil) sun-dried tomatoes, you'll need to soak them in warm water in a small bowl for 30 minutes or until they're soft. Once the tomatoes are soft, remove them from the bowl but don't discard the water. (See the notes below for ways you can use the leftover tomato water.)
Add the chickpeas, 5 sun-dried tomatoes, 5 large basil leaves, 1 small garlic clove, ¼ tsp cumin, ¼ tsp salt, ¼ tsp pepper, 3 tbsp lemon juice, and 1 tbsp water to a food processor. Blend on high until the hummus is smooth and creamy.
In a large pan, saute the diced onion in 3-4 tbsp vegetable broth until the onions are soft and translucent. Add more broth if the pan gets too dry.
While the onions are cooking, boil water in a large pot and cook the noodles. When the noodles are done cooking, carefully reserve 1 cup of the hot pasta water and drain the rest.
Add the hummus, ¾ cup of the reserved pasta water (add more if necessary), and 4 big handfuls of fresh spinach to the pan with the onions. Mix it well to combine the hummus with the water to make the sauce. It will look like a lot of spinach but it will wilt and shrink down after a few minutes.
Add the cooked noodles to the pan with the sauce and mix it all together so the sauce coats every noodle. If the sauce is too thick, add the last ¼ cup of the hot pasta water to thin the sauce. Garnish with more fresh basil before serving.