Place chicken breast on baking sheet. Drizzle with oil and then sprinkle with salt, pepper, garlic powder and paprika.
Bake in 400°F oven for 30 to 35 minutes or until juices run clear. Let stand for 10 minutes. Slice crosswise.
Spread each slice of bread with 1 tbsp hummus.
On one slice of bread, layer avocado, watercress, reserved chicken, tomato and sunflower seeds.
Sandwich with second slice of bread. Serve.