1In a medium pot, combine the beet with water to cover. Salt lightly and bring to a boil. Cook forabout 20 minutes, then remove from the water and set aside to cool.
2Using a mandoline, first slice the cucumber into very thin strings. Then slice the beet (The cucumber is first, since the beet will stain the mandoline.)
3In a small measuring cup, mix together the olive oil, lemon juice, and mint. Add salt and pepper to taste. Whisk until the mixture is emulsified. It should look opaque, with a bright yellow/green color.
4In each of 2 salad bowls, place strings of cucumber and beet. Try to give as much height and dimension as possible—you could even use tweezers.
5Shave 1/2 tablespoon bottarga on top of each cucumber/beet serving. Lightly sprinkle each serving with the dressing. Garnish with lemon zest on top, and serve.