Preheat the oven to 375 degrees F.

Heat a non-stick skillet over medium-high on the stove top and add the chicken sausage. Cook, stirring frequently, until cooked through, about 5 to 8 minutes.

Add the kale and cover the skillet. Cook until wilted, about 2 to 3 minutes.

Crack the eggs into a mixing bowl and whisk them until well-beaten. Whisk in the sea salt.

Transfer the sausage and kale mixture to a lightly oiled (or sprayed) casserole dish and evenly sprinkle the tomatoes and feta cheese over the sausage and kale.

Pour the beaten eggs over everything and use a cooking spoon to gently stir until it appears as though all ingredients are evenly distributed.

Bake on the center rack of the preheated oven for 32 to 40 minutes, or until the eggs have set up and the edges of the casserole are golden-brown.

Allow casserole to cool 10 minutes before slicing and serving.