Glazed Onions

Ingredients:
For the onions
1 1/2 cups water
2 bunches (about 10 total) spring onions, green stems trimmed, peeled and pared to a similar size
1/2 teaspoon sugar
Kosher salt
1 tart apple, such as Granny Smith or Lodi
Sherry vinegar (optional)
For the lime salt (optional)
Finely grated zest of 1 large lime (no pith)
1/4 cup Maldon sea salt or fleur de sel

Directions:
1. For the onions: Combine the water, onions, and sugar; season lightly with salt. Swish the mixture around to mix well; when the water has come to a boil, reduce the heat to medium and cook uncovered for about 20 minutes so the water is bubbling mostly at the edges and checking occasionally to make sure the water is not bubbling too vigorously; if it seems to be jostling the onions too much, reduce the heat as needed.
2. While the onions are cooking, make the lime salt, if desired: Combine the zest and salt, mixing evenly, in a small bowl or freezable container with a tight-fitting lid.
3. When the water is almost gone from the saucepan, peel and core the apple then cut it into 8 wedges. If desired, use a paring knife to trim or turn those wedges so they resemble slim footballs, with tapering ends. Add to the saucepan and toss gently to coat. Cook for a few minutes until they have softened; by this time the onions should be tender enough to offer no resistance when the tip of a knife is inserted.
4. If any layers of onions have dislodged during cooking, discard them.
5. Add a dash of the vinegar, if desired; just enough to add flavor but not enough to make the onions taste like vinegar. Stir to coat.
6. Divide among individual plates; serve warm, with a sprinkle of the lime salt, if desired.