Whip up a creamy avocado spread with lemon, mayo, and yogurt, then layer it with juicy tomato, crisp lettuce, and red onion for a fresh, satisfying sandwich ready in minutes.
Slice the tomato and red onion and rinse the lettuce leaves; pat dry.
In a medium bowl, mash the avocado with a fork. Stir in lemon juice, mayonnaise, Greek yogurt, salt, black pepper, and red pepper flakes (if using) until creamy.
Taste and adjust seasoning with more salt, pepper, or lemon to your liking.
Lay out the bread slices. Spread the creamy avocado mixture evenly over all slices.
Top two slices with tomato, red onion, and lettuce. Cap with the remaining bread slices, spread side down.
Gently press, slice in half if desired, and serve immediately.
Notes
For a vegan version, use vegan mayo and skip the yogurt. Add turkey or crispy bacon for extra protein. To keep the avocado spread green, press plastic wrap directly onto its surface and refrigerate for up to 1 day.