Heat oven to 375°F and arrange a rack in the middle. Line a baking sheet with parchment paper. Melt 2 tablespoons of the butter in a large frying pan over medium-high heat. Add Serrano chile, onion, and salt. Cook, stirring occasionally, until soft, about 5 minutes. Remove from heat and let cool.

Combine flour, baking powder, lime zest, tomatoes, and queso in a large bowl. Add cooled onion mixture and stir to combine.

Using a box grater, grate the remaining butter through the large holes into the flour mixture. Toss the shreds of butter into the flour to coat.

Make a well in the middle of the mixture and pour in the crema. Using a wooden spoon, combine the mixture until it is a shaggy mass. Turn out onto a lightly floured surface and gently knead into a ball. Roll the ball into a 1 1/2-inch thick circle.

Transfer circle to the parchment-lined baking sheet and cut into 12 scones with a sharp knife. You can leave the circle intact if you like a more doughy scone or separate each triangle about 2-inches apart if you like them more crunchy on the outside. Brush the tops with more crema and place in the oven.

Bake for 25-30 minutes or until golden and baked through. Let cool for at least 15 minutes before serving.