Wash and clean 2 cucumbers thoroughly under cold water.

Trim both ends of the cucumbers and remove any rough skin.

Cut the cucumbers in half lengthwise and slice into 1.5 cm thick pieces.

Place cucumber slices in a mixing bowl and sprinkle with 1 tsp salt. Mix well and let sit for 10 minutes.

Slice 1/4 onion and chop green onions into small pieces.

After 10 minutes, drain excess water from the cucumbers.

Add sliced onion, chopped green onions, 1 tsp minced garlic, 1 tbsp soy sauce, 1 tbsp sugar, 1 tbsp vinegar, 1 tbsp plum extract, and 2 tbsp red pepper flakes to the cucumbers.

Drizzle 1 tsp sesame oil and sprinkle 1 tsp sesame seeds. Mix gently with a spoon.