For the raspberry coulis (adapted from "Baking at Home" by the Culinary Institute of America):
Combine the raspberries, 3/4 cup sugar, and 1 tablespoon lemon juice in a saucepan. Bring to a simmer over medium heat, and simmer until the sugar has dissolved, about 10 minutes. Taste the mixture, and if it is too tart for your liking, add more sugar (about 1/4 cup more). Continue to heat until any additional sugar is dissolved.
Strain the coulis through a fine-mesh sieve. Adjust the flavor by adding additional lemon juice if necessary. The coulis can be served warm or cold. It will thicken slightly when stored in the refrigerator and can keep chilled for up to 10 days.
For the labneh:
Between 1 and 2 days ahead of time, lay a piece of fine muslin or cheesecloth over a large bowl and spoon in the yogurt, then stir in the lemon zest. Gather the corners of the cloth together and hang the yogurt above the bowl, leaving it to drip. (You could use a skewer or a cord or rope -- just be careful with pets and little ones). The labneh will form a round, sliceable cake.
Once the labneh has drained and is cake-like, move to a platter and top with the raspberry coulis. Serve with toasted baguettes (see below) or shortbread.
To toast baguettes: Preheat the oven to 350° F, and line a baking sheet with parchment paper. Thinly slice the baguette and brush each piece with soft, unsalted butter. Bake about 15 minutes, until the slices are very lightly browned. The bread should be crisp on the outside, but tender on the inside. Remove from the oven. The bread will finish crisping up as it cools.