Set a large deep pot or Dutch oven over medium heat and add the olive oil. Once the oil shimmers, add the sliced garlic and cook for about 60 to 90 seconds, stirring often, just until it is fragrant and barely golden at the edges. Do not let it brown all the way or it will taste bitter.

Add the zucchini, salt, pepper, and Italian seasoning. Stir everything together and cook for 2 minutes so the zucchini picks up some of that garlic flavor and starts to soften slightly at the edges.

Pour in the vegetable broth and bring it to a full boil over high heat. Once it is boiling, add the dry penne and stir immediately so the pasta does not stick together at the bottom.

Reduce the heat to medium-high and cook the pasta uncovered for 9 to 10 minutes, stirring every 2 minutes or so. You want most of the broth to absorb by the time the pasta is al dente. If it looks dry before the pasta is tender, add broth in quarter-cup splashes. If there is too much liquid left when the pasta is done, just keep cooking and stirring for another minute or two.

Once the pasta is al dente and the broth has mostly absorbed into a light, starchy sauce, stir in the cannellini beans and baby spinach. Cook for about 1 to 2 minutes, just until the spinach is wilted and the beans are warmed through.

Remove the pot from heat and stir in the lemon juice and grated Parmesan. Taste and adjust salt as needed. Add red pepper flakes if you like a little heat. Serve immediately with extra Parmesan on the side.