Halve the tofu block lengthwise, then cut each half into 4 squares, each about 2.5 cm (1 inch) thick. Lay the pieces on a double layer of paper towels, cover with more towels, set a plate on top and weigh it down with a couple of cans. Leave for 15 minutes.
Whisk the miso, sugar, soy sauce, vinegar, oil and ginger in a shallow bowl until it forms a thick paste you can brush.
In a large bowl, whisk the orange juice, zest, olive oil, mustard, salt and pepper. Toss in the beet wedges and set aside.
Move the oven rack to the position closest to the broiler and heat the broiler to high, 290°C (550°F), for about 5 minutes. Line a rimmed baking sheet with foil and brush it with oil.
Pat the tofu dry once more and toss in the glaze until every side is coated. Arrange 2.5 cm (1 inch) apart on the sheet.
Broil 3 to 5 minutes, until the tops are golden brown with a few darker spots. Stay at the oven, since tofu can burn within a minute.
Turn each piece and broil 2 to 5 minutes more, until the edges are golden and crisp.
Pile the arugula onto plates, spoon the beets on top, set the tofu over them, and finish with scallion and sesame seeds.