Coast or Parry's Jepsonia (Jepsonia parryi)
https://www.inaturalist.org/observations/19204295

Willis Linn Jepson was a giant in the world of botany. His 1925 book A Manual of the Flowering Plants of California was the forerunner of The Jepson Manual, the weighty tome used by many botanists today. The book that bears his name may be big and heavy, but the plants that bear his name are small and dainty. The genus Jepsonia includes three species, but only J. parryi occurs in San Diego County. It can be easy to overlook Coast Jepsonia. The tiny white flowers with dark veins pop up in the fall at the end of a bare stem often on clay soil, on north-facing slopes amid rocks or scrubby vegetation. It is even easier to miss the usually single roundish leaf that follows weeks later and appears to emerge from the ground without a stem. Although usually hysteranthous (flowers open before leaves), sometimes a plant will have flowers and leaf present at the same time, as in this observation of the month posted by @rangerwild. In the hot dry summer, the flowers and leaves disappear, but once you find a location with Coast Jepsonia present, you can expect to find it there again in the next wet season when it reappears from an underground stem. Jepsonia parryi can be found from the coast to the inland foothills in San Diego County. It also occurs in Orange and Riverside Counties and Baja California. The diminutive stature and short above-ground lifespan of Jepsonia parryi belie its significance as a plant bearing the name of a giant from the world of botany.