Sauté: Add the oil to a large dutch oven or heavy bottomed pot and warm over medium high heat. Add the onion and sauté for 5 to 7 minutes, stirring occasionally, until it begins to brown on the edges. Reduce the heat to medium.

Aromatics: Add the garlic and black pepper to the pot and saute for 1 minute, until fragrant. Then, add the zucchini and potatoes to the pot; give everything a good mix, then let the veggies sear on the bottom of the pot for 3 minutes, until beginning to brown. Mix well, then let sear for another 3 minutes.

Simmer: Add the vegetable broth to the pan to deglaze it, using a spatula to scrape any browned bits off of the bottom of the pan. Add the water to the pot as well and bring the mixture to a boil over high heat. Once boiling, reduce the heat to medium and simmer for 15 to 18 minutes, stirring occasionally. The soup is done when the zucchini looks translucent and the potatoes can be easily pierced with a fork.

Blend: Carefully transfer the soup to a blender with a venting lid. Add the fresh basil and lemon juice to the soup, then blend on high for 45 to 60 seconds, until smooth. If your blender is on the smaller side you may need to blend the soup in 2 batches.

Serve & Store: Return the soup to the pot to warm if necessary; season with salt and pepper to taste. Serve warm, topped with croutons, parmesan, and a drizzle of olive oil, or as desired. Store any leftovers in the refrigerator in an airtight container for up to 5 days, or in the freezer for up to 2 months.