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 completely.

Once cool, blend oil in food processor on low speed to chop marigold leaves. Into Mason jar, pour marigold oil, close lid, and set aside in a cool, dark place overnight.

In medium-sized bowl, combine tomatoes, baguette, onion, 2 Tbsp olive oil, 2 Tbsp marigold oil, almond flour, vinegar, water, salt, and pepper. Allow to stand at room temperature for 30 minutes, stirring occasionally.

Into blender container, pour contents of bowl and purée. Add watermelon and blend on highest speed until smooth. Pour into individual serving glasses; garnish with a few drops of remaining marigold oil and a few marigold blossoms.