Prep the bread: Heat oven to 425°F (220°C). Arrange bread slices on a sheet pan.
Brush lightly with olive oil and bake 5–7 minutes until lightly golden on top. Set aside.
Sauté aromatics: In a skillet over medium heat, warm 1 tablespoon olive oil. Add onion and a pinch of salt.
Cook 3–4 minutes until soft. Stir in garlic for 30 seconds until fragrant.
Add spinach: Stir in spinach and cook until wilted, about 1–2 minutes. If using frozen, add it directly and cook off extra moisture.
Remove from heat and let cool slightly.
Make the mixture: In a bowl, combine cream cheese, sour cream (or yogurt), mozzarella, Parmesan, lemon zest, lemon juice, red pepper flakes (if using), salt, and pepper. Mix until smooth.
Fold in veggies: Add chopped artichokes and the cooled spinach mixture. Stir until evenly combined.
Taste and adjust seasoning—add more lemon, salt, or pepper as needed.
Top the toasts: Spoon a generous mound of the mixture onto each toasted slice. Sprinkle a little extra mozzarella or Parmesan on top for extra browning.
Broil or bake: Return to the oven. Bake at 425°F for 8–10 minutes, or broil on high 2–4 minutes, until the tops are bubbling and lightly browned.
Watch closely to avoid burning.
Serve: Finish with a crack of black pepper and a squeeze of lemon if you like. Serve hot.