2 medium yellow summer squash, ends trimmed
2 medium zucchini, ends trimmed
1 tablespoon plus ½ teaspoon kosher salt
1 tablespoon sesame seeds
¼ cup tahini
2 tablespoons fresh lemon juice
2 teaspoons toasted sesame oil
1 teaspoon rice vinegar
2 garlic cloves, finely chopped
½-inch piece fresh ginger, peeled (use the edge of a teaspoon to scrape off the skin) and grated
¼ teaspoon chile oil or ¼ teaspoon cayenne pepper
1. Place one of the summer squash on a cutting board. Cut a thin lengthwise slice off one side, then turn the squash so the cut-side faces down (this helps balance the squash so it doesn't roll). Slice the squash lengthwise into ¼- to ⅛-inch-thick planks. Lay the planks flat on the cutting board and slice lengthwise into ¼- to ⅛-inch-thick strips. Place in a medium bowl and repeat with the remaining summer squash and zucchini.
2. Fill a bowl with ice and water and set aside. Fill a saucepan with water, add 1 tablespoon of the salt and bring to a boil over high heat. Add the squash strips and cook until limp, 1 to 1½ minutes. Use tongs to transfer the squash to the ice-water bath (save 2 tablespoons of cooking water and discard the rest). Once the squash is cool, drain in a colander and shake off any excess liquid, then turn the strips onto a kitchen-towel-lined plate and chill in the refrigerator.
3. In a small skillet set over medium heat, toast the sesame seeds, shaking the pan often, until the sesame seeds are golden and fragrant, about 4 to 6 minutes. Transfer to a small plate and set aside.
4. In a medium bowl, whisk together the tahini, the reserved cooking liquid from the squash, lemon juice, sesame oil, rice vinegar, garlic, ginger, chile oil or cayenne pepper and the remaining ½ teaspoon of salt.
5. Remove the squash from the refrigerator and place in a medium bowl. Pour the sesame sauce over the squash and use tongs to gently toss to coat. Serve sprinkled with toasted sesame seeds.