Make the vinaigrette. In a small container, combine the shallots, lemon juice, rice vinegar, olive oil, salt and pepper. Shake to blend.
Place the arugula in a large serving bowl with the onion. Peel the oranges, and use a paring knife to remove all of the white pith from the outside of the fruit. Cut the oranges crosswise into slices, and cut those slices into 4 pieces. Add these to the bowl. Pour the dressing on the salad, and toss to combine. Scatter the pomegranate seeds over the top and serve.
Notes
You can buy pre-shelled pomegranate seeds in little containers in the produce section of the supermarket, or if you’re feeling industrious buy a whole pomegranate, split it apart and remove the seeds yourself. It’s messy but slightly therapeutic work. If you have kids, lay out lots of paper on the table, put them in big t-shirts that can get messy, and let them take on this project. If you live in a place where it’s warm enough to do this outside—definitely go outside.You can also do this in a bowl of cold water, preferably placed in the sink, which help the pomegranate seeds release from the white pithy membrane that ensconces them.