Pat the chicken dry and season both sides with salt, black pepper, and paprika or Italian seasoning.
Heat olive oil in a skillet over medium heat.
Cook the chicken for 5–6 minutes per side, until golden and fully cooked through.
Remove from heat and let rest for 5 minutes, then slice against the grain.
Add spinach to a large bowl and top with tomatoes, cucumber, and red onion.
Whisk dressing ingredients together and drizzle lightly over the salad; toss gently.
Place warm sliced chicken on top of the salad.
Add optional toppings if using and serve immediately.