Using a mandoline or wide-blade box grater, shred the zucchini lengthwise into ribbons. Place ribbons on kitchen towels and salt the zucchini. Let drain 30 minutes then pat dry.
 
Line a 10x14-inch baking sheet with parchment paper, letting the edges hang over a couple of inches on each side. Scatter the zucchini on the baking sheet and toss with sliced onion and garlic. Arrange in even but not-too-organized layer and sprinkle with chili flakes.

 
Combine flour, sugar and 1/2 teaspoon of salt in a mixing bowl.
 
In another large mixing bowl, whisk up eggs, milk and cheese. Whisk the dry ingredients into the eggs and pour batter evenly over the zucchini all the way to the edges of the pan. Drizzle tart with a little EVOO and bake 20-30 minutes until golden and puffed.
 
Cool and cut into 8 large squares.

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