Beet Tostadas With Fried Eggs

Name: Beet Tostadas With Fried Eggs
Ingredients: 1½ lb. red beets (about 2 large), peeled, cut into (¼) pieces; 2 garlic cloves, finely grated; 2 Tbsp. ancho chile powder; 1 tsp. crushed dried oregano, preferably Mexican; 1 tsp. paprika; ¾ tsp. ground cumin; ½ tsp. freshly ground black pepper; 1 Tbsp. Diamond Crystal or 1½ tsp. Morton kosher salt, plus more; 2⅓ cups plus 3 Tbsp. vegetable oil, divided; 1 large white onion, halved through root end, sliced (¼ thick); 6 medium serrano chiles, quartered lengthwise, leaving stems and seeds intact; ⅓ cup sage leaves; 6 (6-diameter) corn tortillas; 6 large eggs; Salsa de Árbol (for serving)