Step 1If the tempura is fresh, set the pieces in a single layer on a wire rack to keep them crisp. If the tempura has been refrigerated, reheat in a toaster oven or an oven set to 400 degrees until crisp, 7 to 10 minutes. Cut into 1-inch-wide strips, if needed.
Step 2Meanwhile, whisk the tempura sauce, vinegar, chile and oil until well mixed.
Step 3Divide the tempura and avocado slices among the lettuce leaves. Drizzle the sauce all over, then top with the pepitas and rice crackers. Serve immediately.
Shrimp Tempura and Avocado Lettuce Wraps: Substitute 6 shrimp tempura for the vegetable tempura, cutting off the tails and slicing each piece crosswise in half.