Add the lemon juice, wholegrain mustard, honey and sea salt flakes to a bowl. Whisk to combine.
Slowly begin pouring in the extra virgin olive oil into the mustard mixture while continually whisking.
Keep whisk until the olive oil and mustard mixture have emulsified, meaning that the lemon juice and olive oil should no longer separate. The dressing will be glossy.
Add cracked black pepper to taste and whisk to combine.
Notes
Storage
Store the salad dressing in a sealed glass jar or airtight container in the fridge for up to two weeks. The dressing will slightly solidify in the fridge, to use just sit the dressing at room temperature until it is liquified. Alternatively you can place the salad dressing in it's container with the lid on in a small bowl of warm water.