Whirl 1 large heirloom tomato (8 oz., chopped) in a blender until smooth. Strain into a cocktail shaker half-filled with ice. Add 1/2 cup potato vodka such as Blue Ice, 1 tsp. grated fresh horseradish, and juice from 1 lemon and shake to blend. Strain into 2 highball glasses. To garnish each glass, thread 3 pitted green olives onto a long Thai chile and set over glass.