Preheat the oven to 400 degrees Fahrenheit/200 degrees Celsius. Wash and pierce the beet peel before wrapping it in foil. Put the wrapped beet in a baking dish and bake once the oven has reached temperature.
Roast the beet for 50-60 minutes, or until a knife can be inserted into the center without resistance (ie it seems tender). Remove from the oven and allow to cool. You may prepare this a day or two ahead of time and refrigerate the cooked beet.
To prepare dressing
In a small dish or jar, combine the oil, lemon juice, vinegar, mustard, sugar, salt, and pepper. If in a bowl, mix together these ingredients first to assist blend.
The shallot should be finely diced or minced, and the tarragon should be finely chopped. Add both to the dressing and, if using a jar, shake to combine. Stir the tarragon and shallot into the dressing to evenly distribute.
To prepare salad
Remove any tough stem/knot regions from the cooked and cooled beet. Cut the beet into slices and then into quarters or smaller/larger pieces as desired to get bite-sized chunks.
Put the greens in two different spots (or one larger platter). Serve with beet slices, pine nuts, and crumbled goat cheese on top. Drizzle with dressing (either the one listed above or your own) and serve.