Follow these steps to create your Smoked Salmon Pizza:

1. Preheat Oven: If your crust requires baking, preheat your oven to 425°F (220°C).
2. Prepare Cream Cheese Mixture: In a small bowl, combine the softened cream cheese, capers, dill, and lemon juice. Mix until well combined and smooth.
3. Assemble Pizza Base: Place the pre-baked pizza crust on a baking sheet or pizza stone.
4. Spread Cream Cheese: Evenly spread the cream cheese mixture over the pizza crust, leaving a small border around the edges.
5. Layer Smoked Salmon: Arrange the smoked salmon slices evenly over the cream cheese layer, overlapping if needed.
6. Add Onions: Scatter the thinly sliced red onions over the smoked salmon.
7. Bake: If your crust needs heating, bake the pizza for 8-10 minutes, or until warmed through and slightly golden at the edges.
8. Top with Greens: Remove the pizza from the oven and top with arugula or baby spinach.
9. Season and Drizzle: Finish with a drizzle of olive oil, a sprinkle of freshly ground black pepper, and extra dill if desired.
10. Slice and Serve: Slice the pizza into wedges and serve immediately.

This straightforward method will guide you to creating a wonderful pizza experience.