Preheat the skillet to medium heat. Slice the cucumber into 1/8 inch thick slices. In a small bowl, combine the yogurt, olive oil, spicy harissa, and stir together with a spoon. Add ¼ teaspoon lemon zest and ¼ teaspoon lemon juice to the spicy harissa yogurt sauce and stir. Taste and adjust heat level as desired.
Spray the pan with a small amount of avocado cooking oil spray. Place the frozen Original Veggie BUBBA burgers directly into the skillet on the stovetop. Cook according to package directions, 5 to 7 minutes per side turning once and cooking until the internal temperature is 165°F.
When the Original Veggie BUBBA burgers have finished cooking, toast the burger buns, cut side down in the skillet for 1 to 2 minutes until golden brown.
Place the bottom burger buns on the serving platter. Top each bottom bun with a tablespoon of the spicy harissa yogurt sauce. Add a few sliced cucumbers, followed by the Original Veggie BUBBA burgers for each bun. Add a leaf of fresh green leaf lettuce, and finish with the toasted top buns. Enjoy!