I can't have the sauce be red, since the people eating this are sensitive to high acidity. :(
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Alfredo and pesto would be my choiceVery low acidity with lots of flavor.
either one or a combination of whipped ricotta and mascarpone (with salt&pepper, spices or herbs to your liking) would be lovely as white pizza sauces as well, especially topped with something like zucchini ribbons (and flowers, if you can get your hands on them!).and a tomato sauce made of slow roasted cherry tomatoes will be much sweeter than a regular red sauce, too.
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A pesto would be good too - standard basil pesto, or maybe an arugula or spinach one, with summer veggies and blobs of some sort of yum cheese ...