Cut kernels from husked corn. Use a large chef’s knife to scrape the milk from the corn cob into a small bowl; discard the cob. Heat 1 tablespoon oil in a medium skillet over medium-high heat. Add the corn kernels; cook, undisturbed, until starting to brown, about 3 minutes. Continue to cook, stirring occasionally, until most kernels are charred, 5 to 7 minutes more. Transfer to the bowl with the corn milk; set aside to cool completely, about 15 minutes.
Add softened butter, sliced chives, grated garlic and ¼ teaspoon salt to the corn mixture; stir to combine.
Spread about 2½ tablespoons corn butter over each slice of toast. Arrange halved tomato slices on top of the corn butter. Sprinkle with ¼ teaspoon flaky salt. Garnish with chives and pepper, if desired.
