Combine the olive oil, 2 tablespoons lemon juice, oregano, garlic powder, salt, and pepper in a bowl. Add the chicken and marinate for at least 30 minutes or up to 4 hours in the refrigerator.
Prepare the tzatziki: In a small bowl, mix the Greek yogurt, grated and squeezed cucumber, minced garlic, dill, 1 tablespoon lemon juice, and 1/4 teaspoon salt. Stir well and refrigerate until serving.
Grill or pan-sear the marinated chicken over medium-high heat until fully cooked, about 6-8 minutes per side, depending on thickness. Let the chicken rest for 5 minutes before slicing against the grain.
Assemble the bowls: Divide the cauliflower rice among serving bowls. Top with sliced chicken.
Add the toppings: Distribute the feta cheese, black olives, and fresh chopped cucumber over the chicken.
Spoon a generous amount of the prepared keto tzatziki sauce over each bowl. Garnish with fresh parsley before serving.
Notes
Squeeze the grated cucumber very firmly to remove excess water; this prevents the tzatziki from becoming watery.
For meal prepping, store the chicken, cauliflower rice, and tzatziki sauce separately. Assemble just before eating.
If you prefer a richer flavor, use chicken thighs instead of breasts.