Pull petals from marigold flowers; snip off and discard white ends. Place petals in small saucepan with 1/4 cup olive oil. Warm gently on low for 5 minutes. Remove from heat and allow oil to cool.
Blend tomatoes, watermelon, red onion, almond flour, sherry vinegar, water, salt, and pepper in a blender until smooth.
Strain the mixture through a fine-mesh sieve to remove any solids.
Chill the gazpacho for at least 30 minutes.
Serve chilled, garnished with marigold blossoms and a drizzle of the infused olive oil.