Step 1

Combine 1/4 cup olive oil, shallot, lemon juice, salt, thyme, garlic, and pepper flakes in large bowl.

Step 2

Pat zucchini very dry with paper towels (this is important!). Heat remaining tablespoon olive oil in 12-inch nonstick skillet until shimmering. Add half of zucchini, cut side down, and sear until golden brown, about 3 minutes. Flip and sear other side. Remove to cutting board and repeat with remaining zucchini.

Step 3

Slice zucchini crosswise into 1/4-inch slices. Transfer to bowl with marinade and toss gently to coat. Allow to marinate for at least 1 hour before serving.

Step 4

Zucchini can be prepared up to 24 hours in advance and stored in the fridge. If refrigerating, allow to sit for about 30 minutes and season with salt before serving. Leftovers keep well for several days.

Step 5

Sprinkle with Parmesan before serving, if using.