Preheat the oven to 425 degrees F=220 degrees celsius. Drain the lentils and put into a pot and cover with water. Bring to a boil on med-high and then turn heat down and simmer until tender (This only takes about 5-10 minutes).
Season the salmon fillets with a little pepper before wrapping them in the prosciutto slices. You can either wrap them whole or, wrap in the middle of the fillets, leaving some of the flesh exposed. Drizzle with olive oil and roast in the oven for around 10 minutes until the prosciutto is golden.
While the salmon is in the oven and the lentils are simmering, season the plain yogurt with salt and pepper to your liking. Also go ahead and chop up all your herbs.
Drain away the water from the lentils and season carefully with salt, pepper, the lemon juice and olive oil. Just before serving, stir the herbs and spinach into the lentils on a high heat, until wilted. Divide the lentils among 4 plates. Place a salmon fillet on top of your pile of lentils, and finish with a drizzle of lightly seasoned yogurt.