Slice the cucumbers into coins about 1/8 inch thick. A mandoline makes this quick and even, but a sharp knife works fine. Place the slices in a medium bowl, sprinkle with the kosher salt, and toss to coat. Let them sit for 10 minutes. You will see liquid pooling at the bottom of the bowl. That is exactly what you want.

While the cucumbers rest, warm the honey. You can microwave it for 10 to 15 seconds in a small bowl or set the jar in a cup of warm water for a minute. It just needs to be pourable and not cold. Whisk the warmed honey together with the apple cider vinegar, water, and black pepper in a small bowl until fully combined and you do not see any honey sitting at the bottom.

Drain the cucumbers. Tilt the bowl and press gently with your hand or a folded paper towel to squeeze out as much liquid as you can. This step keeps the brine from getting too watered down, so do not skip it.

Add the drained cucumbers and the sliced red onion to a quart jar or an airtight container. Pour the honey vinegar brine over the top. Press the cucumbers down gently with a spoon so they are mostly submerged. If any cucumbers are sticking up above the liquid, just press them down, they will settle as they chill.

Seal the jar or container and refrigerate for at least 1 hour. For the best flavor, give it 3 to 4 hours or overnight. The brine will turn slightly cloudy and the cucumbers will soften just a little at the edges while the centers stay crisp.

Right before serving, stir in the torn fresh mint leaves. Adding them at the end keeps them bright green and fragrant. Taste the brine and adjust with a tiny pinch of salt or a small drizzle more honey if you want it a bit sweeter. Serve cold, straight from the jar or spooned into a bowl.