Grate the cucumber on the large holes of a box grater and place in a fine-mesh strainer or cheesecloth fitted over a bowl. Salt the cucumber and let it sit 10 minutes. Thoroughly squeeze out any excess moisture using the cheesecloth or a towel.
Add the drained cucumber to a bowl with the yogurt, harissa, lemon juice, honey, garlic and some pepper. Taste and adjust the seasoning if necessary.