Thinly slice peeled kohlrabi and set aside.
Melt butter in a heavy skillet over medium-high heat. Add onions and sauté until translucent.
Add kohlrabi slices and dried thyme to the skillet with the sautéed onions and gently stir to coat the kohlrabi slices with butter.
Reduce the heat to medium/medium-low and cook for about 15 minutes, turning occasionally, until the kohlrabi is tender and golden.
Serve hot. Top with grated parmesan cheese if desired.